EVALUATING EXTREMELY LOW FREQUENCY MAGNETIC FIELDS IN THE REAR SEATS OF THE ELECTRIC VEHICLES

EVALUATING EXTREMELY LOW FREQUENCY MAGNETIC FIELDS IN THE REAR SEATS OF THE ELECTRIC VEHICLES Abstract In the electric vehicles (EVs), children can sit on a safety seat installed in the rear seats. Owing to their smaller physical dimensions, their heads, generally, are closer to the underfloor electrical systems where the magnetic field (MF) exposure is the greatest. In this study, the magnetic flux density (B) was measured in the rear seats of 10 different EVs, for different driving sessions. We used the measurement results from different heights corresponding to the locations of the heads of an adult and an infant to calculate the induced electric field (E-field) strength using anatomical human models. The results revealed that measured B fields in the rear seats were far below the reference levels by the International Commission on Non-Ionizing Radiation Protection. Although small children may be exposed to higher MF strength, induced E-field strengths were much lower than that of adults due to their particular physical dimensions. INTRODUCTION Electric vehicles (EVs) have become more popular in recent years. EVs eliminates exhaust emissions in urban areas which offers many important benefits to society including lower levels of local pollution and carbon dioxide emissions, and reduced consumption of non-renewable resources. However, the powertrain of EVs usually needs significant electrical power (on the order of several to hundreds of kilowatts(1)). Given the compact space in the cabin of many EVs, occupants can be close to electrical powertrain components, including high-power electrical machines, inverters and high-voltage power cables. Inevitably, extremely low frequency (ELF, frequency range >0–100 kHz(2)) magnetic fields (MF) are generated by the operation of these systems. A factor influencing this study was the reported correlation between ELF MF exposure and the incidence of leukemia(2). To protect against excessive exposure to ELF MF, International Commission on Non-Ionizing Radiation Protection (ICNIRP) has proposed guidelines to establish safety limits for the ELF MF exposures(3). The guidelines use induced electric field (E-field) strength (99th percentile value, E99) as basic restrictions, while magnetic field strength (H) and magnetic flux density (B) are designated as reference levels for use in exposure compliance assessments. The reference levels are numerically derived from the basic restrictions by theoretical simulations using anatomically detailed adult models(4, 5). They are believed to be conservative for judging compliance with the guidelines. The reference levels are also believed to be conservative for children because the induced current density and E-field strength correlated directly with the cross-section area (CSA) perpendicular to the MF polarization (Faraday’s law of electromagnetic induction). Larger physical dimensions usually indicate much higher induced E-field strength. Small children and infants sitting in a safety seat at the rear part of the vehicle is a common occurrence. Children have smaller physical dimensions and, thus, their heads are generally much closer to the car floor, where the MF strength has been reported to be higher due to tire magnetization and the operation of the underfloor electrical systems(6, 7). The matter of children being potentially subject to greater magnetic field exposure may be relevant as leukemia is the most common type of childhood cancer(8). In particular, Ahlbom et al.(9) and Greenland et al.(10) indicated that the exposure to 50 and 60 Hz MF exceeding 0.3–0.4 μT may result in an increased risk for childhood leukemia although a satisfactory causal relationship has not yet been reliably demonstrated. Also, it was reported that a combination of weak, steady and alternating MF could modify the radical concentration, which had the potential to lead to biologically significant changes(11). In this study, we measured the ELF MF at the rear seats for ten types of EVs. The B field was measured at four points along the centerline of the rear seats. Four typical driving scenarios including stationary, acceleration, deceleration and driving with a constant speed, were employed in the measurements. Through statistical analysis, the worst-case exposure scenario was identified and frequency domain measurements were performed for the scenario. The measured B field at different heights corresponding to the physique of an adult and a small child were implemented in the numerical simulations to calculate in situ E-field strengths for comparison to the ICNIRP basic restrictions. An infant model(12) and an adult model(13) were used in the simulations. The measurement results demonstrated that the acceleration/deceleration sessions can introduce the highest B fields but the values were still far below the ICNIRP reference levels. The induced E-field strength was lower for the child model although the child’s head may be exposed to a greater MF strength. This work is the first study to evaluate the potential ELF MF exposure for children in EVs with realistic measured values. METHODS AND MATERIALS Measurement protocols EV samples Overall, 10 EVs of different types (Table 1) were selected for MF measurement. They were manufactured between 2014 and 2017. They were popular in Chinese markets(14) and were among the bestselling types of EVs for the first half of 2017 according to market survey reports(15). Table 1. EVs under test. Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Table 1. EVs under test. Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Measurement equipment Both broadband and frequency domain measurements were performed using the ELF MF meter (SEM-600, Safetytech, Beijing, China) equipped with an ELF MF probe (LF-01, Safetytech, Beijing, China). The probe and the field meter were connected by an optic cable. The frequency range of the probe was 1 Hz–100 kHz and its measurement range was 0.01 nT–10 mT. All of the measurement instruments were recently calibrated (07/07/2017). The measurement system fulfilled the requirement of EN 50 492-2009(16) and ICNIRP guidelines(3, 17). During the measurement, the probe was held stationary when the vehicle moved. An acceleration sensor (LIS3LV02DL, STMicroelectronics, Geneva, Switzerland) was used to record the acceleration/deceleration rate. A holder made of plastic foam was used to fix the probe and a drawing of the holder is shown in Figure 1a and b. The dielectric loss tangent of the foam holder was <5%. Figure 1. View largeDownload slide Schematic of the probe supporter (a), magnetic flux density measurement for head level of the child (b), pelvis level (c) and ankle level of the adult (d). Figure 1. View largeDownload slide Schematic of the probe supporter (a), magnetic flux density measurement for head level of the child (b), pelvis level (c) and ankle level of the adult (d). Measurement specifications Both broadband and frequency domain measurements were performed in the study. At first, we recorded the broadband values at the 4 points shown in Figure 1a. The points represented the head height of an adult (#1) and a small child (#2), adult pelvis (#3) and ankle (#4) of the adult, respectively. The pelvic region was roughly the same regardless of the age group of the occupants. The ankle region was only available for the adult occupants because children have shorter legs and can put their feet on the seat. The measurement at each point lasted for 60 s, including the four vehicle operational scenarios, i.e. 20 s of stationary while switch-on, 20 s of driving with a speed of 40 km/h (with a permissible variation up to ±15%), 10 s of acceleration at the rate of 2.2 m/s2 and 10 s of deceleration at the same rate. Each point was repetitively measured a total of five times. During measurement, the sequence of the four scenarios was randomly ordered to avoid any potential operator induced influence from the previous sessions. During the broadband measurements, the meter sampled with three mutually orthogonal sensing coils, and reported the B field components, respectively. We set the sampling time for the broadband meter at 1 s. Subsequently, we performed the frequency domain measurement only for the worst-case driving scenarios (reporting the highest B field results) that would correlate with the highest induced E-field strength. The frequency domain measurement reported the spectral components (SCs) of B components per 1 s. Ultimately, the measured values were used to calculate the induced E-field within the anatomical models. Most of the available studies reported the spectrum of EV below 2 kHz(18–20) although the spectrum was highly dependent on the specific driving sessions and can be as high as to several hundred kHz(21). In the present research, we focused on this frequency band as well (for both the broadband and the frequency domain measurements). During the experiments, the seats in the front row were center-positioned. The rear seats were in their rearmost position. The headrests were in the full-back position. The seat backs, except for the rearmost seats, were 15° back from the vertical. Before each test, all the electronics in the vehicle were switched on for more than 5 min, including the lights, heater and air conditioner, radio, demister (a device incorporating a heater and/or blower used in a vehicle to free the windscreen of condensation that removes condensation), front and rear wipers. The configurations for EVs complied with the requirements of the International Electrotechnical Commission (IEC)(22). Test environments The experiments were performed on Shuguang West Road in Chaoyang District, Beijing during 01/08/2017 to 07/08/2017. The length of the road used for the tests was 1.5 km (Figure 2) and the elevation varied only 5 m. The road was generally straight with relatively low automobile traffic flow (0.2 vehicle passing per second during the experiments). As such, the EVs under test could keep a stable and pre-programmed driving condition during the experiments. We performed the experiments with the humidity at 45–75% and the temperature ranging from 31 to 34°C. There were no high-voltage power lines along the road. The mean background field strength was 0.03 μT (broadband value: 1 Hz–2 kHz) while the peak value was <0.1 μT. During the experiments, the municipal traffic regulations were respected. Figure 2. View largeDownload slide Test location. Figure 2. View largeDownload slide Test location. Statistical analysis for the broadband results In order to determine the worst-case driving scenario, the broadband values were subject to a 4 × 4 repeated measures analyses of variance (ANOVA). The variables were the driving scenarios (stationary while switched on, S1; 40 km/h driving, S2; acceleration, S3 and deceleration, S4) and the measurement points (#1, #2, #3 and #4, see Figure 1a). Greenhouse–Geisser adjustment was applied to correct the degrees of freedom if the assumption of sphericity failed (by Mauchly’s test). When the differences of average levels among the four scenarios or of the four points are statistically significant, multiple comparisons are performed. The Bonferroni correction was applied to minimize the likelihood of a type I error. The SPSS software package, version 21.0 was used for statistical analysis in the study. Numerical computations using the anatomical models The anatomical models representing an adult female (1.56 m, 22 years old, Figure 3a)(13) and an infant (0.74 m in height, 12-month-old male, Figure 3b)(12) were used in the numerical simulations. Free-form deformation(23) was conducted to achieve a sitting posture for the models. The models are shown in Figure 3. For the sitting posture, the adult head was at the level of the headrest (#1) while position #2 was approximately at the height level of the infant head. Figure 3. View largeDownload slide Anatomical models for the infant and the adult. (a) Adult female model, (b) infant model, (c) adult model sitting on the seat and (d) infant sitting on the seat. Figure 3. View largeDownload slide Anatomical models for the infant and the adult. (a) Adult female model, (b) infant model, (c) adult model sitting on the seat and (d) infant sitting on the seat. The measured B field values at locations #1 and #2 were applied for numerical simulations. Hence, we could assess the dosimetric influence due to the physical difference in anatomy. In order to report the maximal induced E-field strength in the anatomical models, the measured values from the worst-case scenario were used for simulations because higher B values could induce higher E-field strength. To note, higher B gradient might also lead to higher local E-field results due to the voxelization of the model. We did not consider it in the study. In the work, we used the scalar potential finite element method (SPFE)(24) to evaluate the MF exposure. SPFE is based on quasi-static approximation and was implemented by SEMCAD-X v14.8. A uniform magnetic field exposure scenario was assumed for the simulations. The MF orientation was perpendicular to the coronal plane of the human model, which was assumed so that the highest induced E-field due to the larger CSA, compared with those on the sagittal and transverse planes, could be achieved(25). The computational volume was voxelised to 2 mm × 2 mm × 2 mm. Zero Neumann conditions (vanishing normal flux) were applied in the quasi-static magnetic simulations. Automatic termination of the simulation was set as ten orders of magnitude reduction from the initial value. To calculate the E-field strength induced by MF exposure with multiple SCs, we performed simulation for each SC separately and combined the derived E-field by the following equation: Ei,(x,y,z)=Ef1,i,(x,y,z)+Ef2,i,(x,y,z)+⋯+Efn,i,(x,y,z) (1) where, (x, y, z) represents the Cartesian coordinates of the studied voxel in the human body; i = 1, 2, 3 represents three orthogonal field components; f1, f2, … fn are the frequency components of the exposure signals. Equation (1) assumes that the induced E-field values are additive in phase and the summation is performed over 2 mm × 2 mm × 2 mm voxels. E99 was presented by filtering the 1% voxels with the highest induced E-field values in the 2 mm × 2 mm × 2 mm voxels. E99 for the central nerve system (E99_CNS) and the peripheral nervous system (E99_PNS), proposed by ICNIRP(3), were used as the metrics in the present study. The frequency-dependent tissue conductivity was from the database of Gabriel et al.(26) and can be extracted from the Internet database of Italian National Research Council. RESULTS EVs used in the study were arbitrarily designated as EV1–EV10 to protect the commercial interest of the manufacturers. Measured broadband results The broadband results for each measured position of the left and right rear seats are reported in Table 2 in terms of geometric mean (GM) and geometric standard deviation (GSD) of the RMS magnetic flux density. The GM gives the same weighting to all the observations and, thus, demonstrates its applicability for comparing the MF strength in EVs(27, 28). Table 2. GM and GSD of broadband B values (RMS) for all the measurement points. The format of the data is GM (GSD). Unit: μT RMS. Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Table 2. GM and GSD of broadband B values (RMS) for all the measurement points. The format of the data is GM (GSD). Unit: μT RMS. Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) A principal feature of the measured MF was the significant fluctuation range of the values (a variation as great as 100 times can be found between the consecutive time observations). Statistical analysis for the broadband values A significant difference for the interaction effect between driving scenarios and measurement points was found (F(9, 351) = 2.48, p = 0.0094). As well, a significant difference for the four measurement points was detected (F(3, 117) = 3.96, p = 0.0099). The multiple comparison demonstrated that the B field values measured at location #4 (floor in from of rear seat) were the highest, followed by values from location #3 (rear seat cushion), #2 (child’s head position) and #1 (adult’s head position) (p < 0.012, α = 0.05/3 = 0.017). There was a significant difference between the driving scenarios (F(3, 117) = 3.72, p = 0.013). The acceleration and deceleration scenarios generated higher B fields compared with the stationary and the 40 km/h driving scenarios (p < 0.01, α = 0.05/3 = 0.017) while no difference was identified between acceleration and deceleration (p = 0.16). Frequency domain results We used the measurement values from locations #1 and #2 to evaluate the MF exposure in the EVs corresponding to the height of the adult and child head respectively. We plot SCs in these scenarios for locations #1 and #2 (1–2000 Hz, amplitude no <0.01 μT were recorded) with the interval of 1 s in Figure 4. This figure demonstrates that the frequencies for the SCs of #1 and #2 are not the same. It is reasonable because #1 and #2 may be close to different electric devices and the specific magnetic field emission may alter the spectrum. Other factors may also contribute to the effect, e.g. the measurement uncertainty as well as the operation of the electrified systems: a slight touch on the brake or the accelerator can substantially modify the spectrum. Since the minimal sampling time of the probe was 1 s, there was the possibility that the instantaneous B values could exceed the reported range. Figure 4. View largeDownload slide Measured SCs during the acceleration and deceleration sessions at #1 and #2. Figure 4. View largeDownload slide Measured SCs during the acceleration and deceleration sessions at #1 and #2. We calculated the GM for the amplitude and the frequency of the measured scenarios at #1 and #2. The results are listed in Table 3. The maximal values of the measurements are also presented in the same table. Table 3. Measured SCs during the acceleration and deacceleration sessions. Unit: μT RMS. GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / Amp, amplitude; Freq, frequency. Var (%) is presented by the percentage of increase for GM value on position #2 compared with the values on position #1. Table 3. Measured SCs during the acceleration and deacceleration sessions. Unit: μT RMS. GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / Amp, amplitude; Freq, frequency. Var (%) is presented by the percentage of increase for GM value on position #2 compared with the values on position #1. Induced E-field for the infant and the adult models The E99 calculated for the respective B-field values are shown in Table 4. The results demonstrate that the induced E-field strength was lower for the infant model compared with that of the adult in terms of both the head and body as a whole. Table 4. Magnetic flux density for simulating the uniform MF exposure. CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 Var (%) is presented by the percentage of increase for adult value compared with infant value. Table 4. Magnetic flux density for simulating the uniform MF exposure. CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 Var (%) is presented by the percentage of increase for adult value compared with infant value. DICUSSIONS For the surveyed EVs, the maximal traction power was different, ranging from 41.8 to 160 kW. However, no significant difference was observed in the measured data. The reason is likely to be the moderate acceleration rate (2.2 m/s2) applied in the experiments. In this mode of acceleration/deceleration, EVs under test need not output the maximal power so that no obviously higher MF values were found even for the EVs with much higher power. A more rapid acceleration might produce higher MF magnitudes but we did not try it for three reasons. Firstly, the route was not closed for the driving test; excessive acceleration may pose a potential threat to the passengers and passing vehicles. Secondly, the moderate acceleration provided a relatively long time to accelerate before the EV reached the maximal permitted velocity of the route. Thirdly, acceleration from 0 to 80 km/h within 100 m (around 2.2 m/s2) is a prerequisite for the Chinese driving license test and we deemed that this acceleration rate was typical for practical driving. Again, we need to remind the possibility that the instantaneous B values could exceed the reported range because the measurement probe could not sample faster than 1 s. Although several SCs on higher frequencies have been observed (can spread to 1.24 kHz), the spectral analysis revealed that the SCs concentrated on bands below 1000 Hz. The EVs under test used aluminum alloy wheel rims, which have low magnetic permeability. However, the steel wire in the reinforcing belts of radial tires pick up magnetic fields from the terrestrial MF. When the tires spin, the magnetized steel wire in the reinforcing belts generates ELF MF usually below 20 Hz, that can exceed 2.0 μT at seat level in the passenger compartment(6). The measurement did not identify the ELF MF by different sources because the purpose of the study was to investigate the realistic exposure scenario for the occupants. To note, degaussing the tires or using the fiberglass belted tires can eliminate this effect and provide the MF results solely introduced by the operation of the electrified system. SCs changed rapidly during the acceleration/deceleration periods and posed a challenge to evaluate the induced E-field. We selected the maximal SC measured in 1-s intervals with orientation perpendicular to the largest CSA of the human body. The time interval corresponded to the requirement of the standard for evaluating the MF in EVs(22). The scenario was assumed to induce the highest E-field strength(25). In Table 3, the MF GM level measured at an infant head (#2) higher than those measured for an adult head (#1) by 4.45–5.45% for the three SCs, while the maximum measured level was 9.38–10.99% higher. In Table 4, our finding indicated that the discrepancy in CSA between the child and the adult was so large (head CSA of the infant was 34.79% less than that of the adult) that the resultant difference could not be counterbalanced by the difference in MF flux density at the head level of the adult and the child (as shown in Table 3, GM and maximal B values increased 4.45–5.45% and 9.38–10.99% for the infant’s head compared with that of the adult). The discrepancy in body CSA was even larger (around 1:3.4) and it was reasonable to see that the adult had higher E99_PNS when sitting on the seat. In the study, we used only one infant model but the results were shown to be representative. As shown from the statistical analysis of the measured B field values along the centerline of the rear seat, lower positions indicated higher B field results. The reason can be attributed to operation of the high-power cables beneath the floor. We used the model of an infant of only 12 months old, which had a very low height. Therefore, the infant’s head was exposed to the highest MF strength. Using a larger child model, its head may approach point #1, where the B field was lower. In summary, the presented induced E-field strength results in an infant model are deemed to being conservative. The infant was reported to have higher electrical conductivity(29) but there was no database dedicated to the infant. Furthermore, below 1 MHz, the database was hard to be measured and the uncertainty was large(30). Therefore, we would not include the issue in the study. To note, the investigation for the dosimetric effect of the enhanced electrical conductivity could be conducted through a statistical approach(31) and deserves further study. ICNIRP proposed guidelines to evaluate the compliance of the non-sinusoidal signal exposure(3). The measurements rendered the maximal B field at the level of one-tenth to several μT, far below the reference level of the guidelines (e.g. 200 μT for 20–400 Hz). The similar non-sinusoidal MF signal magnitudes can only account for 6–10% of the reference levels according to the previous reports(32). However, as noted in the Introduction, ‘… 50 and 60 Hz MF exceeding 0.3–0.4 μT may result in an increased risk for childhood leukemia’. Therefore, it is necessary to measure the MF in the EVs to limit the exposure and for the purpose of epidemiological studies. CONCLUSION In this study, we measured ELF MF in the rear seats of ten types of EVs. The measurements were performed for four different driving scenarios. The measurement results were analyzed to determine the worst-case scenario and those values were used for simulations. We made numerical simulations to compare the induced E-field strength due to the physical difference between children and adults using detailed anatomical models. The results support the contention that the MF in the EVs that we tested was far below the reference levels of the ICNIRP guidelines. Furthermore, our findings show that children would not be more highly exposed compared to adults when taking into consideration of their physical differences. However, the measurement results indicated that further studies should be performed to elucidate the concerns on the incidence of the childhood leukemia for infant and child occupants. FUNDING This work was supported by grants from National Natural Science Foundation Project (Grant No. 61371187 and 61671158) and National Science and Technology Major Project (No. 2018ZX10301201). REFERENCES 1 de Santiago , J. , Bernhoff , H. , Ekergård , B. , Eriksson , S. , Ferhatovic , S. , Waters , R. and Leijon , M. Electrical motor drivelines in commercial all-electric vehicles: a review . IEEE Trans. Veh. Technol. 61 ( 2 ), 475 – 484 ( 2012 ). Google Scholar CrossRef Search ADS 2 World Health Organization (WHO) . Electromagnetic Fields and Public Health: Exposure to Extremely Low Frequency Fields ( 2007 ). Available on http://www.who.int/peh-emf/publications/facts/fs322/en/. 3 International Commission on Non-Ionizing Radiation Protection (ICNIRP) . Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz) . Health Phys. 99 ( 6 ), 818 – 836 ( 2010 ). PubMed 4 Dimbylow , P. Development of the female voxel phantom, NAOMI, and its application to calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields . Phys. Med. Biol. 50 ( 6 ), 1047 – 1070 ( 2005 ). Google Scholar CrossRef Search ADS PubMed 5 Dimbylow , P. Development of pregnant female, hybrid voxel-mathematical models and their application to the dosimetry of applied magnetic and electric fields at 50 Hz . Phys. Med. Biol. 51 ( 10 ), 2383 – 2394 ( 2006 ). Google Scholar CrossRef Search ADS PubMed 6 Milham , S. , Hatfield , J. B. and Tell , R. Magnetic fields from steel-belted radial tires: implications for epidemiological studies . Bioelectromagnetics 20 ( 7 ), 440 – 445 ( 1999 ). Google Scholar CrossRef Search ADS PubMed 7 Stankowski , S. , Kessi , A. , Bécheiraz , O. , Meier-Engel , K. and Meier , M. Low frequency magnetic fields induced by car tire magnetization . Health Phys. 90 ( 2 ), 148 – 153 ( 2006 ). Google Scholar CrossRef Search ADS PubMed 8 National Cancer Institute . Cancer in Children and Adolescents ( 2008 ). Available on (http://www.cancer.gov/cancertopics/factsheet/Sites-Types/childhood). 9 Ahlbom , A. et al. . A pooled analysis of magnetic fields and childhood leukaemia . Br. J. Cancer 83 ( 5 ), 692 – 698 ( 2000 ). Google Scholar CrossRef Search ADS PubMed 10 Greenland , S. , Sheppard , A. R. , Kaune , W. T. , Poole , C. and Kelsh , M. A. A pooled analysis of magnetic fields, wire codes, and childhood leukemia . Epidemiology 11 ( 6 ), 624 – 634 ( 2000 ). Google Scholar CrossRef Search ADS PubMed 11 Barnes , F. S. and Greenebaum , B. The effects of weak magnetic fields on radical pairs . Bioelectromagnetics 36 ( 1 ), 45 – 54 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 12 Li , C. et al. . Generation of infant anatomical models for evaluating electromagnetic field exposures . Bioelectromagnetics 36 ( 1 ), 10 – 26 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 13 Wu , T. , Tan , L. , Shao , Q. , Li , Y. , Yang , L. , Zhao , C. , Xie , Y. and Zhang , S. X. Slice-based supine to standing postured deformation for Chinese anatomical models and the dosimetric results by wide band frequency electromagnetic field exposure: morphing . Radiat. Prot. Dosim. 154 ( 1 ), 26 – 30 ( 2013 ). Google Scholar CrossRef Search ADS 14 Research in China . Global and China Electric Vehicle (BEV, PHEV) Industry Report, 2016–2020. Research in China 2016, pp. 1–152 ( 2016 ). 15 Wynand , G. The Chinese New Energy Vehicle Market China EV Sales for H1 2017. WATTEV2BUY.2017.6.12. Available on http://wattev2buy.com/chinese-new-energy-vehicle-market-china-ev-sales-h1-2017/ ( 2017 ). 16 NF EN 50492-2009 Standard . CENELEC—En 50492 basic Standard for the In-Situ Measurement of Electromagnetic Field Strength Related to Human Exposure in The Vicinity of Base Stations. 17 International Commission on Non-Ionizing Radiation Protection (ICNIRP) . Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz) . Health Phys. 74 ( 4 ), 494 – 522 ( 1998 ). PubMed 18 Dietrich , F. M. and Jacobs , W. L. Survey and assessment of electric and magnetic field (EMF) public exposure in the transportation environment (No. PB-99-130908/XAB). Electric Research and Management, Inc., State College, PA (United States); John A. Volpe National Transportation Systems Center, Cambridge, MA ( 1999 ). 19 Schmid , G. , Überbacher , R. and Göth , P. ELF and LF magnetic field exposure in hybrid-and electric cars. In: Proc. Bio-electromagnetics Conf. 9–3 ( 2009 ). 20 Ruddle , A. R. , Low , L. and Vassilev , A. Evaluating low frequency magnetic field exposure from traction current transients in electric vehicles. In: 2013 International Symposium on Electromagnetic Compatibility (EMC EUROPE). pp. 78–83 ( 2013 ). 21 Tell , R. A. and Kavet , R. Electric and magnetic fields <100 kHz in electric and gasoline-powered vehicles . Radiat. Prot. Dosim. 172 ( 4 ), 541 – 546 ( 2017 ). Google Scholar CrossRef Search ADS 22 International Electrotechnical Commission (IEC) . Determining Procedures for the Measurement of Field Levels Generated by Electronic and Electrical Equipment in the Automotive Environment With Respect to Human Exposure ( Geneva : IEC Webstsore ) ( 2016 ) IEC:TC 106/PT 62764-1. 23 Li , C. and Wu , T. Dosimetry of infant exposure to power-frequency magnetic fields: variation of 99th percentile induced electric field value by posture and skin-to-skin contact . Bioelectromagnetics 36 ( 3 ), 204 – 218 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 24 Biro , O. and Preis , K. On the use of the magnetic vector potential in the finite-element analysis of three-dimensional eddy currents . IEEE Trans. Magn. 25 ( 4 ), 3145 – 3159 ( 1989 ). Google Scholar CrossRef Search ADS 25 Dimbylow , P. J. and Findlay , R. The effects of body posture, anatomy, age and pregnancy on the calculation of induced current densities at 50 Hz . Radiat. Prot. Dosim. 139 ( 4 ), 532 – 538 ( 2010 ). Google Scholar CrossRef Search ADS 26 Gabriel , S. , Lau , R. W. and Gabriel , C. The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz . Phys. Med. Biol. 41 ( 11 ), 2251 – 2269 ( 1996 ). Google Scholar CrossRef Search ADS PubMed 27 Ronen , H. , Madhuri , S. , Malka , N. H. , Yoav , Y. , Yuval , T. , Daniel , N. and Leeka , K. Characterization of extremely low frequency magnetic fields from diesel, gasoline and hybrid cars under controlled conditions . Int. J. Environ. Res. Public Health 12 ( 2 ), 1651 – 1666 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 28 Tell , R. A. , Sias , G. , Smith , J. , Sahl , J. and Kavet , R. ELF magnetic fields in electric and gasoline-powered vehicles . Bioelectromagnetics 34 ( 2 ), 156 – 161 ( 2013 ). Google Scholar CrossRef Search ADS PubMed 29 Peyman , A. Dielectric properties of tissues; variation with age and their relevance in exposure of children to electromagnetic fields; state of knowledge . Prog. Biophys. Mol. Biol. 107 ( 3 ), 434 – 438 ( 2011 ). Google Scholar CrossRef Search ADS PubMed 30 Gabriel , C. , Peyman , A. and Grant , E. H. Electrical conductivity of tissue at frequencies below 1 MHz . Phys. Med. Biol. 54 ( 16 ), 4863 – 4878 ( 2009 ). Google Scholar CrossRef Search ADS PubMed 31 Šušnjara , A. and Poljak , D. An efficient deterministic-stochastic model of the human body exposed to ELF electric field . Int. J. Antenn. Propag. 2016 , 1 – 8 ( 2016 ). Google Scholar CrossRef Search ADS 32 Vassilev , A. , Ferber , A. , Wehrmann , C. , Pinaud , O. , Schilling , Meinhard and Ruddle , A. R. Magnetic field exposure assessment in electric vehicles . IEEE Trans. Electromagn. C 57 ( 1 ), 35 – 43 ( 2015 ). Google Scholar CrossRef Search ADS © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

EVALUATING EXTREMELY LOW FREQUENCY MAGNETIC FIELDS IN THE REAR SEATS OF THE ELECTRIC VEHICLES

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© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
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Abstract

Abstract In the electric vehicles (EVs), children can sit on a safety seat installed in the rear seats. Owing to their smaller physical dimensions, their heads, generally, are closer to the underfloor electrical systems where the magnetic field (MF) exposure is the greatest. In this study, the magnetic flux density (B) was measured in the rear seats of 10 different EVs, for different driving sessions. We used the measurement results from different heights corresponding to the locations of the heads of an adult and an infant to calculate the induced electric field (E-field) strength using anatomical human models. The results revealed that measured B fields in the rear seats were far below the reference levels by the International Commission on Non-Ionizing Radiation Protection. Although small children may be exposed to higher MF strength, induced E-field strengths were much lower than that of adults due to their particular physical dimensions. INTRODUCTION Electric vehicles (EVs) have become more popular in recent years. EVs eliminates exhaust emissions in urban areas which offers many important benefits to society including lower levels of local pollution and carbon dioxide emissions, and reduced consumption of non-renewable resources. However, the powertrain of EVs usually needs significant electrical power (on the order of several to hundreds of kilowatts(1)). Given the compact space in the cabin of many EVs, occupants can be close to electrical powertrain components, including high-power electrical machines, inverters and high-voltage power cables. Inevitably, extremely low frequency (ELF, frequency range >0–100 kHz(2)) magnetic fields (MF) are generated by the operation of these systems. A factor influencing this study was the reported correlation between ELF MF exposure and the incidence of leukemia(2). To protect against excessive exposure to ELF MF, International Commission on Non-Ionizing Radiation Protection (ICNIRP) has proposed guidelines to establish safety limits for the ELF MF exposures(3). The guidelines use induced electric field (E-field) strength (99th percentile value, E99) as basic restrictions, while magnetic field strength (H) and magnetic flux density (B) are designated as reference levels for use in exposure compliance assessments. The reference levels are numerically derived from the basic restrictions by theoretical simulations using anatomically detailed adult models(4, 5). They are believed to be conservative for judging compliance with the guidelines. The reference levels are also believed to be conservative for children because the induced current density and E-field strength correlated directly with the cross-section area (CSA) perpendicular to the MF polarization (Faraday’s law of electromagnetic induction). Larger physical dimensions usually indicate much higher induced E-field strength. Small children and infants sitting in a safety seat at the rear part of the vehicle is a common occurrence. Children have smaller physical dimensions and, thus, their heads are generally much closer to the car floor, where the MF strength has been reported to be higher due to tire magnetization and the operation of the underfloor electrical systems(6, 7). The matter of children being potentially subject to greater magnetic field exposure may be relevant as leukemia is the most common type of childhood cancer(8). In particular, Ahlbom et al.(9) and Greenland et al.(10) indicated that the exposure to 50 and 60 Hz MF exceeding 0.3–0.4 μT may result in an increased risk for childhood leukemia although a satisfactory causal relationship has not yet been reliably demonstrated. Also, it was reported that a combination of weak, steady and alternating MF could modify the radical concentration, which had the potential to lead to biologically significant changes(11). In this study, we measured the ELF MF at the rear seats for ten types of EVs. The B field was measured at four points along the centerline of the rear seats. Four typical driving scenarios including stationary, acceleration, deceleration and driving with a constant speed, were employed in the measurements. Through statistical analysis, the worst-case exposure scenario was identified and frequency domain measurements were performed for the scenario. The measured B field at different heights corresponding to the physique of an adult and a small child were implemented in the numerical simulations to calculate in situ E-field strengths for comparison to the ICNIRP basic restrictions. An infant model(12) and an adult model(13) were used in the simulations. The measurement results demonstrated that the acceleration/deceleration sessions can introduce the highest B fields but the values were still far below the ICNIRP reference levels. The induced E-field strength was lower for the child model although the child’s head may be exposed to a greater MF strength. This work is the first study to evaluate the potential ELF MF exposure for children in EVs with realistic measured values. METHODS AND MATERIALS Measurement protocols EV samples Overall, 10 EVs of different types (Table 1) were selected for MF measurement. They were manufactured between 2014 and 2017. They were popular in Chinese markets(14) and were among the bestselling types of EVs for the first half of 2017 according to market survey reports(15). Table 1. EVs under test. Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Table 1. EVs under test. Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Manufacturer Type Frame number Maximal power (kW) Net weight of EV (kg) Total weight of EV (kg) Chery Automobile EQ LVVDB17B3GB120050 41.8 1128 1196.2 Beijing Automotive EV160 LNBSCB3FOFD112474 45 1295 1363.2 Beijing Automotive EV200 LNBSCB3F2GD112851 53 1295 1363.2 Beijing Automotive EX200 LNBSCU3HOGR734719 53 1360 1428.2 Jianghuai Automobile iEV4 LJ1EFKRN5G4200613 60 1260 1328.2 Jianghuai Automobile iEV5 LJ1EFKRP4G4006995 60 1260 1328.2 Dongfeng Motor Group Venucia e30 LNBSCU3HOGR734719 80 1010 1078.2 BYD E6 JingYU8442 (temporary license) 120 2295 2363.2 BYD E5 LGXCE6DB2G0079780 160 1845 1913.2 BYD QIN LGXCE6CC9G0021983 160 1900 1968.2 Measurement equipment Both broadband and frequency domain measurements were performed using the ELF MF meter (SEM-600, Safetytech, Beijing, China) equipped with an ELF MF probe (LF-01, Safetytech, Beijing, China). The probe and the field meter were connected by an optic cable. The frequency range of the probe was 1 Hz–100 kHz and its measurement range was 0.01 nT–10 mT. All of the measurement instruments were recently calibrated (07/07/2017). The measurement system fulfilled the requirement of EN 50 492-2009(16) and ICNIRP guidelines(3, 17). During the measurement, the probe was held stationary when the vehicle moved. An acceleration sensor (LIS3LV02DL, STMicroelectronics, Geneva, Switzerland) was used to record the acceleration/deceleration rate. A holder made of plastic foam was used to fix the probe and a drawing of the holder is shown in Figure 1a and b. The dielectric loss tangent of the foam holder was <5%. Figure 1. View largeDownload slide Schematic of the probe supporter (a), magnetic flux density measurement for head level of the child (b), pelvis level (c) and ankle level of the adult (d). Figure 1. View largeDownload slide Schematic of the probe supporter (a), magnetic flux density measurement for head level of the child (b), pelvis level (c) and ankle level of the adult (d). Measurement specifications Both broadband and frequency domain measurements were performed in the study. At first, we recorded the broadband values at the 4 points shown in Figure 1a. The points represented the head height of an adult (#1) and a small child (#2), adult pelvis (#3) and ankle (#4) of the adult, respectively. The pelvic region was roughly the same regardless of the age group of the occupants. The ankle region was only available for the adult occupants because children have shorter legs and can put their feet on the seat. The measurement at each point lasted for 60 s, including the four vehicle operational scenarios, i.e. 20 s of stationary while switch-on, 20 s of driving with a speed of 40 km/h (with a permissible variation up to ±15%), 10 s of acceleration at the rate of 2.2 m/s2 and 10 s of deceleration at the same rate. Each point was repetitively measured a total of five times. During measurement, the sequence of the four scenarios was randomly ordered to avoid any potential operator induced influence from the previous sessions. During the broadband measurements, the meter sampled with three mutually orthogonal sensing coils, and reported the B field components, respectively. We set the sampling time for the broadband meter at 1 s. Subsequently, we performed the frequency domain measurement only for the worst-case driving scenarios (reporting the highest B field results) that would correlate with the highest induced E-field strength. The frequency domain measurement reported the spectral components (SCs) of B components per 1 s. Ultimately, the measured values were used to calculate the induced E-field within the anatomical models. Most of the available studies reported the spectrum of EV below 2 kHz(18–20) although the spectrum was highly dependent on the specific driving sessions and can be as high as to several hundred kHz(21). In the present research, we focused on this frequency band as well (for both the broadband and the frequency domain measurements). During the experiments, the seats in the front row were center-positioned. The rear seats were in their rearmost position. The headrests were in the full-back position. The seat backs, except for the rearmost seats, were 15° back from the vertical. Before each test, all the electronics in the vehicle were switched on for more than 5 min, including the lights, heater and air conditioner, radio, demister (a device incorporating a heater and/or blower used in a vehicle to free the windscreen of condensation that removes condensation), front and rear wipers. The configurations for EVs complied with the requirements of the International Electrotechnical Commission (IEC)(22). Test environments The experiments were performed on Shuguang West Road in Chaoyang District, Beijing during 01/08/2017 to 07/08/2017. The length of the road used for the tests was 1.5 km (Figure 2) and the elevation varied only 5 m. The road was generally straight with relatively low automobile traffic flow (0.2 vehicle passing per second during the experiments). As such, the EVs under test could keep a stable and pre-programmed driving condition during the experiments. We performed the experiments with the humidity at 45–75% and the temperature ranging from 31 to 34°C. There were no high-voltage power lines along the road. The mean background field strength was 0.03 μT (broadband value: 1 Hz–2 kHz) while the peak value was <0.1 μT. During the experiments, the municipal traffic regulations were respected. Figure 2. View largeDownload slide Test location. Figure 2. View largeDownload slide Test location. Statistical analysis for the broadband results In order to determine the worst-case driving scenario, the broadband values were subject to a 4 × 4 repeated measures analyses of variance (ANOVA). The variables were the driving scenarios (stationary while switched on, S1; 40 km/h driving, S2; acceleration, S3 and deceleration, S4) and the measurement points (#1, #2, #3 and #4, see Figure 1a). Greenhouse–Geisser adjustment was applied to correct the degrees of freedom if the assumption of sphericity failed (by Mauchly’s test). When the differences of average levels among the four scenarios or of the four points are statistically significant, multiple comparisons are performed. The Bonferroni correction was applied to minimize the likelihood of a type I error. The SPSS software package, version 21.0 was used for statistical analysis in the study. Numerical computations using the anatomical models The anatomical models representing an adult female (1.56 m, 22 years old, Figure 3a)(13) and an infant (0.74 m in height, 12-month-old male, Figure 3b)(12) were used in the numerical simulations. Free-form deformation(23) was conducted to achieve a sitting posture for the models. The models are shown in Figure 3. For the sitting posture, the adult head was at the level of the headrest (#1) while position #2 was approximately at the height level of the infant head. Figure 3. View largeDownload slide Anatomical models for the infant and the adult. (a) Adult female model, (b) infant model, (c) adult model sitting on the seat and (d) infant sitting on the seat. Figure 3. View largeDownload slide Anatomical models for the infant and the adult. (a) Adult female model, (b) infant model, (c) adult model sitting on the seat and (d) infant sitting on the seat. The measured B field values at locations #1 and #2 were applied for numerical simulations. Hence, we could assess the dosimetric influence due to the physical difference in anatomy. In order to report the maximal induced E-field strength in the anatomical models, the measured values from the worst-case scenario were used for simulations because higher B values could induce higher E-field strength. To note, higher B gradient might also lead to higher local E-field results due to the voxelization of the model. We did not consider it in the study. In the work, we used the scalar potential finite element method (SPFE)(24) to evaluate the MF exposure. SPFE is based on quasi-static approximation and was implemented by SEMCAD-X v14.8. A uniform magnetic field exposure scenario was assumed for the simulations. The MF orientation was perpendicular to the coronal plane of the human model, which was assumed so that the highest induced E-field due to the larger CSA, compared with those on the sagittal and transverse planes, could be achieved(25). The computational volume was voxelised to 2 mm × 2 mm × 2 mm. Zero Neumann conditions (vanishing normal flux) were applied in the quasi-static magnetic simulations. Automatic termination of the simulation was set as ten orders of magnitude reduction from the initial value. To calculate the E-field strength induced by MF exposure with multiple SCs, we performed simulation for each SC separately and combined the derived E-field by the following equation: Ei,(x,y,z)=Ef1,i,(x,y,z)+Ef2,i,(x,y,z)+⋯+Efn,i,(x,y,z) (1) where, (x, y, z) represents the Cartesian coordinates of the studied voxel in the human body; i = 1, 2, 3 represents three orthogonal field components; f1, f2, … fn are the frequency components of the exposure signals. Equation (1) assumes that the induced E-field values are additive in phase and the summation is performed over 2 mm × 2 mm × 2 mm voxels. E99 was presented by filtering the 1% voxels with the highest induced E-field values in the 2 mm × 2 mm × 2 mm voxels. E99 for the central nerve system (E99_CNS) and the peripheral nervous system (E99_PNS), proposed by ICNIRP(3), were used as the metrics in the present study. The frequency-dependent tissue conductivity was from the database of Gabriel et al.(26) and can be extracted from the Internet database of Italian National Research Council. RESULTS EVs used in the study were arbitrarily designated as EV1–EV10 to protect the commercial interest of the manufacturers. Measured broadband results The broadband results for each measured position of the left and right rear seats are reported in Table 2 in terms of geometric mean (GM) and geometric standard deviation (GSD) of the RMS magnetic flux density. The GM gives the same weighting to all the observations and, thus, demonstrates its applicability for comparing the MF strength in EVs(27, 28). Table 2. GM and GSD of broadband B values (RMS) for all the measurement points. The format of the data is GM (GSD). Unit: μT RMS. Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Table 2. GM and GSD of broadband B values (RMS) for all the measurement points. The format of the data is GM (GSD). Unit: μT RMS. Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) Stationary Acceleration 40 km/h driving Deceleration #1 Left  EV1 0.092 (1.884) 0.233 (1.494) 0.119 (1.434) 0.167 (1.253)  EV2 0.068 (1.286) 0.180 (1.814) 0.097 (1.660) 0.236 (1.168)  EV3 0.016 (1.546) 0.071 (1.424) 0.021 (1.964) 0.126 (1.769)  EV4 0.054 (1.379) 0.177 (1.266) 0.057 (1.145) 0.203 (1.623)  EV5 0.063 (1.327) 0.231 (1.478) 0.142 (1.397) 0.206 (1.561)  EV6 0.039 (1.365) 0.101 (1.181) 0.081 (1.128) 0.200 (1.155)  EV7 0.020 (1.213) 0.093 (1.194) 0.040 (1.356) 0.082 (1.470)  EV8 0.064 (1.606) 0.398 (1.687) 0.147 (1.262) 0.513 (1.091)  EV9 0.026 (1.243) 0.052 (1.552) 0.015 (1.662) 0.040 (1.696)  EV10 0.049 (1.127) 0.139 (1.962) 0.056 (1.068) 0.136 (1.472) #1 Right  EV1 0.073 (1.071) 0.315 (1.092) 0.101 (1.271) 0.286 (1.464)  EV2 0.039 (1.207) 0.298 (1.627) 0.068 (1.206) 0.230 (1.249)  EV3 0.027 (1.434) 0.098 (1.292) 0.059 (1.547) 0.147 (1.281)  EV4 0.051 (1.568) 0.231 (1.094) 0.082 (1.468) 0.306 (1.365)  EV5 0.073 (1.613) 0.325 (1.432) 0.091 (1.883) 0.302 (1.078)  EV6 0.067 (1.114) 0.303 (1.120) 0.097 (1.285) 0.298 (1.714)  EV7 0.048 (1.288) 0.281 (1.152) 0.050 (1.398) 0.347 (1.083)  EV8 0.079 (1.232) 0.398 (1.347) 0.086 (1.146) 0.540 (1.250)  EV9 0.022 (1.409) 0.095 (1.640) 0.024 (1.226) 0.118 (1.346)  EV10 0.042 (1.286) 0.142 (1.249) 0.065 (1.118) 0.279 (1.285) #2 Left  EV1 0.118 (1.819) 0.297 (1.535) 0.199 (1.699) 0.270 (1.428)  EV2 0.060 (1.640) 0.209 (1.115) 0.109 (1.176) 0.199 (1.369)  EV3 0.037 (1.242) 0.164 (1.724) 0.067 (1.962) 0.281 (1.440)  EV4 0.069 (1.255) 0.197 (1.083) 0.088 (1.387) 0.262 (1.202)  EV5 0.052 (1.942) 0.220 (1.143) 0.124 (1.987) 0.198 (1.140)  EV6 0.045 (1.430) 0.120 (1.321) 0.110 (1.896) 0.251 (1.775)  EV7 0.018 (1.299) 0.092 (1.067) 0.049 (1.187) 0.090 (1.268)  EV8 0.091 (1.352) 0.612 (1.312) 0.243 (1.263) 0.779 (1.066)  EV9 0.029 (1.184) 0.072 (1.731) 0.019 (1.283) 0.048 (1.277)  EV10 0.054 (1.270) 0.188 (1.162) 0.058 (1.086) 0.198 (1.446) #2 Right  EV1 0.033 (1.541) 0.162 (1.098) 0.054 (1.253) 0.139 (1.254)  EV2 0.036 (1.078) 0.228 (1.610) 0.058 (1.787) 0.220 (1.119)  EV3 0.044 (1.539) 0.166 (1.250) 0.111 (1.999) 0.227 (1.262)  EV4 0.062 (1.286) 0.306 (1.723) 0.094 (1.654) 0.413 (1.421)  EV5 0.099 (1.175) 0.426 (1.777) 0.109 (1.494) 0.392 (1.489)  EV6 0.109 (1.114) 0.434 (1.151) 0.183 (1.319) 0.517 (1.790)  EV7 0.049 (1.355) 0.309 (1.077) 0.042 (1.187) 0.315 (1.499)  EV8 0.124 (1.362) 0.667 (1.491) 0.182 (1.146) 0.629 (1.849)  EV9 0.039 (1.129) 0.175 (1.243) 0.047 (1.988) 0.163 (1.325)  EV10 0.061 (1.757) 0.202 (1.234) 0.092 (1.338) 0.374 (1.356) #3 Left  EV1 0.090 (1.516) 0.175 (1.794) 0.122 (1.125) 0.178 (1.804)  EV2 0.102 (1.374) 0.270 (1.339) 0.155 (1.103) 0.476 (1.582)  EV3 0.042 (1.171) 0.176 (1.622) 0.067 (1.474) 0.359 (1.564)  EV4 0.068 (1.628) 0.215 (1.583) 0.072 (1.325) 0.247 (1.944)  EV5 0.052 (1.198) 0.205 (1.113) 0.129 (1.588) 0.221 (1.086)  EV6 0.072 (1.743) 0.208 (1.668) 0.146 (1.222) 0.408 (1.233)  EV7 0.022 (1.309) 0.110 (1.956) 0.050 (1.875) 0.101 (1.378)  EV8 0.077 (1.675) 0.420 (1.337) 0.188 (1.839) 0.561 (1.146)  EV9 0.132 (1.317) 0.304 (1.063) 0.111 (1.647) 0.244 (1.488)  EV10 0.116 (1.427) 0.339 (1.546) 0.116 (1.405) 0.343 (1.313) #3 Right  EV1 0.056 (1.926) 0.327 (1.918) 0.100 (1.368) 0.298 (1.164)  EV2 0.068 (1.132) 0.484 (1.526) 0.091 (1.752) 0.382 (1.613)  EV3 0.062 (1.979) 0.235 (1.603) 0.149 (1.623) 0.396 (1.165)  EV4 0.063 (1.801) 0.246 (1.620) 0.131 (1.468) 0.365 (1.164)  EV5 0.120 (1.507) 0.447 (1.189) 0.126 (1.792) 0.459 (1.554)  EV6 0.106 (1.505) 0.488 (1.722) 0.194 (1.444) 0.495 (1.286)  EV7 0.136 (1.796) 0.870 (1.852) 0.149 (1.164) 0.742 (1.686)  EV8 0.155 (1.661) 0.772 (1.100) 0.212 (1.986) 0.885 (1.282)  EV9 0.043 (1.483) 0.192 (1.781) 0.055 (1.787) 0.177 (1.155)  EV10 0.113 (1.381) 0.412 (1.176) 0.142 (1.521) 0.655 (1.552) #4 Left  EV1 0.381 (1.732) 0.928 (1.672) 0.603 (1.593) 0.793 (1.542)  EV2 0.348 (1.217) 1.183 (1.789) 0.542 (1.517) 1.185 (1.855)  EV3 0.171 (1.365) 0.761 (1.228) 0.255 (1.136) 1.253 (1.483)  EV4 0.296 (1.243) 0.884 (1.697) 0.353 (1.148) 0.935 (1.524)  EV5 0.304 (1.198) 1.382 (1.149) 0.672 (1.271) 1.172 (1.184)  EV6 0.191 (1.303) 0.653 (1.317) 0.382 (1.955) 1.124 (1.466)  EV7 0.252 (1.417) 1.139 (1.339) 0.689 (1.235) 1.320 (1.091)  EV8 0.307 (1.079) 2.251 (1.754) 0.953 (1.211) 2.609 (1.693)  EV9 0.296 (1.218) 0.790 (1.670) 0.192 (1.782) 0.536 (1.757)  EV10 0.289 (1.399) 0.943 (1.818) 0.246 (1.618) 0.823 (1.063) #4 Right  EV1 0.228 (1.618) 1.075 (1.805) 0.369 (1.544) 0.941 (1.532)  EV2 0.225 (1.663) 1.763 (1.614) 0.410 (1.061) 1.407 (1.313)  EV3 0.276 (1.230) 0.894 (1.214) 0.553 (1.200) 1.416 (1.276)  EV4 0.272 (1.110) 1.277 (1.550) 0.499 (1.571) 1.607 (1.223)  EV5 0.307 (1.727) 1.347 (1.132) 0.380 (1.578) 1.626 (1.715)  EV6 0.353 (1.420) 1.640 (1.572) 0.473 (1.262) 1.697 (1.783)  EV7 0.362 (1.109) 2.287 (1.278) 0.341 (1.879) 2.043 (1.781)  EV8 0.362 (1.176) 1.862 (1.279) 0.519 (1.851) 2.005 (1.189)  EV9 0.291 (1.101) 1.166 (1.075) 0.322 (1.084) 1.453 (1.789)  EV10 0.251 (1.255) 0.764 (1.570) 0.344 (1.133) 1.925 (1.357) A principal feature of the measured MF was the significant fluctuation range of the values (a variation as great as 100 times can be found between the consecutive time observations). Statistical analysis for the broadband values A significant difference for the interaction effect between driving scenarios and measurement points was found (F(9, 351) = 2.48, p = 0.0094). As well, a significant difference for the four measurement points was detected (F(3, 117) = 3.96, p = 0.0099). The multiple comparison demonstrated that the B field values measured at location #4 (floor in from of rear seat) were the highest, followed by values from location #3 (rear seat cushion), #2 (child’s head position) and #1 (adult’s head position) (p < 0.012, α = 0.05/3 = 0.017). There was a significant difference between the driving scenarios (F(3, 117) = 3.72, p = 0.013). The acceleration and deceleration scenarios generated higher B fields compared with the stationary and the 40 km/h driving scenarios (p < 0.01, α = 0.05/3 = 0.017) while no difference was identified between acceleration and deceleration (p = 0.16). Frequency domain results We used the measurement values from locations #1 and #2 to evaluate the MF exposure in the EVs corresponding to the height of the adult and child head respectively. We plot SCs in these scenarios for locations #1 and #2 (1–2000 Hz, amplitude no <0.01 μT were recorded) with the interval of 1 s in Figure 4. This figure demonstrates that the frequencies for the SCs of #1 and #2 are not the same. It is reasonable because #1 and #2 may be close to different electric devices and the specific magnetic field emission may alter the spectrum. Other factors may also contribute to the effect, e.g. the measurement uncertainty as well as the operation of the electrified systems: a slight touch on the brake or the accelerator can substantially modify the spectrum. Since the minimal sampling time of the probe was 1 s, there was the possibility that the instantaneous B values could exceed the reported range. Figure 4. View largeDownload slide Measured SCs during the acceleration and deceleration sessions at #1 and #2. Figure 4. View largeDownload slide Measured SCs during the acceleration and deceleration sessions at #1 and #2. We calculated the GM for the amplitude and the frequency of the measured scenarios at #1 and #2. The results are listed in Table 3. The maximal values of the measurements are also presented in the same table. Table 3. Measured SCs during the acceleration and deacceleration sessions. Unit: μT RMS. GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / Amp, amplitude; Freq, frequency. Var (%) is presented by the percentage of increase for GM value on position #2 compared with the values on position #1. Table 3. Measured SCs during the acceleration and deacceleration sessions. Unit: μT RMS. GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / GM Max First SC Second SC Third SC First SC Second SC Third SC Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) Amp (μT) Freq (Hz) #1 0.087 48 0.084 200 0.047 667 1.280 58 0.570 183 0.240 763 #2 0.092 39 0.088 189 0.049 643 1.440 50 0.630 160 0.260 350 Var (%) 5.45 / 4.45 / 4.49 / 10.84 / 9.38 / 10.99 / Amp, amplitude; Freq, frequency. Var (%) is presented by the percentage of increase for GM value on position #2 compared with the values on position #1. Induced E-field for the infant and the adult models The E99 calculated for the respective B-field values are shown in Table 4. The results demonstrate that the induced E-field strength was lower for the infant model compared with that of the adult in terms of both the head and body as a whole. Table 4. Magnetic flux density for simulating the uniform MF exposure. CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 Var (%) is presented by the percentage of increase for adult value compared with infant value. Table 4. Magnetic flux density for simulating the uniform MF exposure. CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 CSA_Head (mm2) E99_CNS (V/m) CSA_Body (mm2) E99_PNS (V/m) GM Max GM Max Infant model 21 768 6.75e-5 7.31e-4 74 728 1.35e-4 1.45e-3 Adult model 29 340 1.02e-4 1.08e-3 251 157 2.18e-4 2.30e-3 Var (%) 34.79 51.11 47.61 236.09 61.48 58.62 Var (%) is presented by the percentage of increase for adult value compared with infant value. DICUSSIONS For the surveyed EVs, the maximal traction power was different, ranging from 41.8 to 160 kW. However, no significant difference was observed in the measured data. The reason is likely to be the moderate acceleration rate (2.2 m/s2) applied in the experiments. In this mode of acceleration/deceleration, EVs under test need not output the maximal power so that no obviously higher MF values were found even for the EVs with much higher power. A more rapid acceleration might produce higher MF magnitudes but we did not try it for three reasons. Firstly, the route was not closed for the driving test; excessive acceleration may pose a potential threat to the passengers and passing vehicles. Secondly, the moderate acceleration provided a relatively long time to accelerate before the EV reached the maximal permitted velocity of the route. Thirdly, acceleration from 0 to 80 km/h within 100 m (around 2.2 m/s2) is a prerequisite for the Chinese driving license test and we deemed that this acceleration rate was typical for practical driving. Again, we need to remind the possibility that the instantaneous B values could exceed the reported range because the measurement probe could not sample faster than 1 s. Although several SCs on higher frequencies have been observed (can spread to 1.24 kHz), the spectral analysis revealed that the SCs concentrated on bands below 1000 Hz. The EVs under test used aluminum alloy wheel rims, which have low magnetic permeability. However, the steel wire in the reinforcing belts of radial tires pick up magnetic fields from the terrestrial MF. When the tires spin, the magnetized steel wire in the reinforcing belts generates ELF MF usually below 20 Hz, that can exceed 2.0 μT at seat level in the passenger compartment(6). The measurement did not identify the ELF MF by different sources because the purpose of the study was to investigate the realistic exposure scenario for the occupants. To note, degaussing the tires or using the fiberglass belted tires can eliminate this effect and provide the MF results solely introduced by the operation of the electrified system. SCs changed rapidly during the acceleration/deceleration periods and posed a challenge to evaluate the induced E-field. We selected the maximal SC measured in 1-s intervals with orientation perpendicular to the largest CSA of the human body. The time interval corresponded to the requirement of the standard for evaluating the MF in EVs(22). The scenario was assumed to induce the highest E-field strength(25). In Table 3, the MF GM level measured at an infant head (#2) higher than those measured for an adult head (#1) by 4.45–5.45% for the three SCs, while the maximum measured level was 9.38–10.99% higher. In Table 4, our finding indicated that the discrepancy in CSA between the child and the adult was so large (head CSA of the infant was 34.79% less than that of the adult) that the resultant difference could not be counterbalanced by the difference in MF flux density at the head level of the adult and the child (as shown in Table 3, GM and maximal B values increased 4.45–5.45% and 9.38–10.99% for the infant’s head compared with that of the adult). The discrepancy in body CSA was even larger (around 1:3.4) and it was reasonable to see that the adult had higher E99_PNS when sitting on the seat. In the study, we used only one infant model but the results were shown to be representative. As shown from the statistical analysis of the measured B field values along the centerline of the rear seat, lower positions indicated higher B field results. The reason can be attributed to operation of the high-power cables beneath the floor. We used the model of an infant of only 12 months old, which had a very low height. Therefore, the infant’s head was exposed to the highest MF strength. Using a larger child model, its head may approach point #1, where the B field was lower. In summary, the presented induced E-field strength results in an infant model are deemed to being conservative. The infant was reported to have higher electrical conductivity(29) but there was no database dedicated to the infant. Furthermore, below 1 MHz, the database was hard to be measured and the uncertainty was large(30). Therefore, we would not include the issue in the study. To note, the investigation for the dosimetric effect of the enhanced electrical conductivity could be conducted through a statistical approach(31) and deserves further study. ICNIRP proposed guidelines to evaluate the compliance of the non-sinusoidal signal exposure(3). The measurements rendered the maximal B field at the level of one-tenth to several μT, far below the reference level of the guidelines (e.g. 200 μT for 20–400 Hz). The similar non-sinusoidal MF signal magnitudes can only account for 6–10% of the reference levels according to the previous reports(32). However, as noted in the Introduction, ‘… 50 and 60 Hz MF exceeding 0.3–0.4 μT may result in an increased risk for childhood leukemia’. Therefore, it is necessary to measure the MF in the EVs to limit the exposure and for the purpose of epidemiological studies. CONCLUSION In this study, we measured ELF MF in the rear seats of ten types of EVs. The measurements were performed for four different driving scenarios. The measurement results were analyzed to determine the worst-case scenario and those values were used for simulations. We made numerical simulations to compare the induced E-field strength due to the physical difference between children and adults using detailed anatomical models. The results support the contention that the MF in the EVs that we tested was far below the reference levels of the ICNIRP guidelines. Furthermore, our findings show that children would not be more highly exposed compared to adults when taking into consideration of their physical differences. However, the measurement results indicated that further studies should be performed to elucidate the concerns on the incidence of the childhood leukemia for infant and child occupants. FUNDING This work was supported by grants from National Natural Science Foundation Project (Grant No. 61371187 and 61671158) and National Science and Technology Major Project (No. 2018ZX10301201). REFERENCES 1 de Santiago , J. , Bernhoff , H. , Ekergård , B. , Eriksson , S. , Ferhatovic , S. , Waters , R. and Leijon , M. Electrical motor drivelines in commercial all-electric vehicles: a review . IEEE Trans. Veh. Technol. 61 ( 2 ), 475 – 484 ( 2012 ). Google Scholar CrossRef Search ADS 2 World Health Organization (WHO) . Electromagnetic Fields and Public Health: Exposure to Extremely Low Frequency Fields ( 2007 ). Available on http://www.who.int/peh-emf/publications/facts/fs322/en/. 3 International Commission on Non-Ionizing Radiation Protection (ICNIRP) . Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz) . Health Phys. 99 ( 6 ), 818 – 836 ( 2010 ). PubMed 4 Dimbylow , P. Development of the female voxel phantom, NAOMI, and its application to calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields . Phys. Med. Biol. 50 ( 6 ), 1047 – 1070 ( 2005 ). Google Scholar CrossRef Search ADS PubMed 5 Dimbylow , P. Development of pregnant female, hybrid voxel-mathematical models and their application to the dosimetry of applied magnetic and electric fields at 50 Hz . Phys. Med. Biol. 51 ( 10 ), 2383 – 2394 ( 2006 ). Google Scholar CrossRef Search ADS PubMed 6 Milham , S. , Hatfield , J. B. and Tell , R. Magnetic fields from steel-belted radial tires: implications for epidemiological studies . Bioelectromagnetics 20 ( 7 ), 440 – 445 ( 1999 ). Google Scholar CrossRef Search ADS PubMed 7 Stankowski , S. , Kessi , A. , Bécheiraz , O. , Meier-Engel , K. and Meier , M. Low frequency magnetic fields induced by car tire magnetization . Health Phys. 90 ( 2 ), 148 – 153 ( 2006 ). Google Scholar CrossRef Search ADS PubMed 8 National Cancer Institute . Cancer in Children and Adolescents ( 2008 ). Available on (http://www.cancer.gov/cancertopics/factsheet/Sites-Types/childhood). 9 Ahlbom , A. et al. . A pooled analysis of magnetic fields and childhood leukaemia . Br. J. Cancer 83 ( 5 ), 692 – 698 ( 2000 ). Google Scholar CrossRef Search ADS PubMed 10 Greenland , S. , Sheppard , A. R. , Kaune , W. T. , Poole , C. and Kelsh , M. A. A pooled analysis of magnetic fields, wire codes, and childhood leukemia . Epidemiology 11 ( 6 ), 624 – 634 ( 2000 ). Google Scholar CrossRef Search ADS PubMed 11 Barnes , F. S. and Greenebaum , B. The effects of weak magnetic fields on radical pairs . Bioelectromagnetics 36 ( 1 ), 45 – 54 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 12 Li , C. et al. . Generation of infant anatomical models for evaluating electromagnetic field exposures . Bioelectromagnetics 36 ( 1 ), 10 – 26 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 13 Wu , T. , Tan , L. , Shao , Q. , Li , Y. , Yang , L. , Zhao , C. , Xie , Y. and Zhang , S. X. Slice-based supine to standing postured deformation for Chinese anatomical models and the dosimetric results by wide band frequency electromagnetic field exposure: morphing . Radiat. Prot. Dosim. 154 ( 1 ), 26 – 30 ( 2013 ). Google Scholar CrossRef Search ADS 14 Research in China . Global and China Electric Vehicle (BEV, PHEV) Industry Report, 2016–2020. Research in China 2016, pp. 1–152 ( 2016 ). 15 Wynand , G. The Chinese New Energy Vehicle Market China EV Sales for H1 2017. WATTEV2BUY.2017.6.12. Available on http://wattev2buy.com/chinese-new-energy-vehicle-market-china-ev-sales-h1-2017/ ( 2017 ). 16 NF EN 50492-2009 Standard . CENELEC—En 50492 basic Standard for the In-Situ Measurement of Electromagnetic Field Strength Related to Human Exposure in The Vicinity of Base Stations. 17 International Commission on Non-Ionizing Radiation Protection (ICNIRP) . Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz) . Health Phys. 74 ( 4 ), 494 – 522 ( 1998 ). PubMed 18 Dietrich , F. M. and Jacobs , W. L. Survey and assessment of electric and magnetic field (EMF) public exposure in the transportation environment (No. PB-99-130908/XAB). Electric Research and Management, Inc., State College, PA (United States); John A. Volpe National Transportation Systems Center, Cambridge, MA ( 1999 ). 19 Schmid , G. , Überbacher , R. and Göth , P. ELF and LF magnetic field exposure in hybrid-and electric cars. In: Proc. Bio-electromagnetics Conf. 9–3 ( 2009 ). 20 Ruddle , A. R. , Low , L. and Vassilev , A. Evaluating low frequency magnetic field exposure from traction current transients in electric vehicles. In: 2013 International Symposium on Electromagnetic Compatibility (EMC EUROPE). pp. 78–83 ( 2013 ). 21 Tell , R. A. and Kavet , R. Electric and magnetic fields <100 kHz in electric and gasoline-powered vehicles . Radiat. Prot. Dosim. 172 ( 4 ), 541 – 546 ( 2017 ). Google Scholar CrossRef Search ADS 22 International Electrotechnical Commission (IEC) . Determining Procedures for the Measurement of Field Levels Generated by Electronic and Electrical Equipment in the Automotive Environment With Respect to Human Exposure ( Geneva : IEC Webstsore ) ( 2016 ) IEC:TC 106/PT 62764-1. 23 Li , C. and Wu , T. Dosimetry of infant exposure to power-frequency magnetic fields: variation of 99th percentile induced electric field value by posture and skin-to-skin contact . Bioelectromagnetics 36 ( 3 ), 204 – 218 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 24 Biro , O. and Preis , K. On the use of the magnetic vector potential in the finite-element analysis of three-dimensional eddy currents . IEEE Trans. Magn. 25 ( 4 ), 3145 – 3159 ( 1989 ). Google Scholar CrossRef Search ADS 25 Dimbylow , P. J. and Findlay , R. The effects of body posture, anatomy, age and pregnancy on the calculation of induced current densities at 50 Hz . Radiat. Prot. Dosim. 139 ( 4 ), 532 – 538 ( 2010 ). Google Scholar CrossRef Search ADS 26 Gabriel , S. , Lau , R. W. and Gabriel , C. The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz . Phys. Med. Biol. 41 ( 11 ), 2251 – 2269 ( 1996 ). Google Scholar CrossRef Search ADS PubMed 27 Ronen , H. , Madhuri , S. , Malka , N. H. , Yoav , Y. , Yuval , T. , Daniel , N. and Leeka , K. Characterization of extremely low frequency magnetic fields from diesel, gasoline and hybrid cars under controlled conditions . Int. J. Environ. Res. Public Health 12 ( 2 ), 1651 – 1666 ( 2015 ). Google Scholar CrossRef Search ADS PubMed 28 Tell , R. A. , Sias , G. , Smith , J. , Sahl , J. and Kavet , R. ELF magnetic fields in electric and gasoline-powered vehicles . Bioelectromagnetics 34 ( 2 ), 156 – 161 ( 2013 ). Google Scholar CrossRef Search ADS PubMed 29 Peyman , A. Dielectric properties of tissues; variation with age and their relevance in exposure of children to electromagnetic fields; state of knowledge . Prog. Biophys. Mol. Biol. 107 ( 3 ), 434 – 438 ( 2011 ). Google Scholar CrossRef Search ADS PubMed 30 Gabriel , C. , Peyman , A. and Grant , E. H. Electrical conductivity of tissue at frequencies below 1 MHz . Phys. Med. Biol. 54 ( 16 ), 4863 – 4878 ( 2009 ). Google Scholar CrossRef Search ADS PubMed 31 Šušnjara , A. and Poljak , D. An efficient deterministic-stochastic model of the human body exposed to ELF electric field . Int. J. Antenn. Propag. 2016 , 1 – 8 ( 2016 ). Google Scholar CrossRef Search ADS 32 Vassilev , A. , Ferber , A. , Wehrmann , C. , Pinaud , O. , Schilling , Meinhard and Ruddle , A. R. Magnetic field exposure assessment in electric vehicles . IEEE Trans. Electromagn. C 57 ( 1 ), 35 – 43 ( 2015 ). Google Scholar CrossRef Search ADS © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Radiation Protection DosimetryOxford University Press

Published: Mar 23, 2018

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