## 5 Discussion  
This study evaluated compliance assessment using the spatial averaging method as a scheme to evaluate human exposure to nonuniform fields at low frequencies. The evaluation index for this method was the spatially averaged magnetic field strength at three or four heights from the ground or floor and the internal electric field in the anatomical human model placed near or inside the vehicle. As shown in Figures 5 and 6, the distributions of the magnetic field were not significantly different between iron and CFRP outside the vehicle. However, the magnetic field was scarcely distributed for a body made of iron placed inside the vehicle. This is because the conductive chassis shields the magnetic field. In contrast, the magnetic field generated by the WPT system for a body made of CFRP leaks directly into the cabin beneath the floor. This resulted in a marginal difference in the internal electric field in the human body outside the vehicle because of the body material, but a significant difference inside the vehicle. We calculated the magnetic field averaged over the heights defined in this study and compared it with the ICNIRP guidelines and IEEE standard in terms of \(a_{c}\). When \(a_{c}\) is less than one, the BR would still be satisfied even with an increased coil output, provided that \(H_{\text{ave}}\) of the definition satisfies the RL. [PERSON] et al. reported a ratio of the internal electric field in the human model, and the total electric field in the human model. Figure 12: Variation of the compliance assessment for each definition when the vehicle seat position was changed in the front–back direction with the vehicle body made of (**a**) iron and (**b**) CFRP. field to the three-point average magnetic field strength of 0.20 V/A with three human body models at several angles outside the vehicle [18], which is close to 0.13 V/A obtained for a similar averaging definition in this study. These values are close but somewhat different from other studies (see Table 1), which is attributable to different postures and target areas discussed in previous studies. Note that the discussion here follows the discussion for the product safety standard (See Section 3.4). As shown in Figure 9, Definition 1 provided a conservative assessment of the ICNIRP guidelines with each body material. However, Definition 1 did not meet the requirements of the IEEE standard, whereas Definitions 2 and 3 were satisfied. This is because RL prescribed in the IEEE standard are relatively tolerant of a permissible external magnetic field. Using Definition 1 and following the ICNIRP guidelines, the maximum permissible transferred power for outside the vehicle made of iron and CFRP was 196 and 191 kW, respectively. Moreover, it was 884 and 871 kW using Definition 2 and the IEEE standard, respectively. The whole-body \(H_{\text{ave}}\), \(H\) at specific points, and three- or four-point \(H_{\text{ave}}\) provided good correlation for the scenario inside the vehicle, whereas no consistent trend was discernible for the other one-point measurement points (Figure 10). This can be attributed to the difficulty of capturing the electric field at a single point in a highly nonuniform environment with a realistic human body shape, such as the driver's posture. Additionally, measuring the magnetic field over the volume of the human body is practically difficult. Therefore, the spatially averaged method is a good index to reasonably simplify the compliance assessment procedure inside the vehicle. As shown in Figure 11, all definitions for the iron body provided a sufficiently conservative assessment of the ICNIRP guidelines, whereas they were either comparable or unconservative with respect to the IEEE standard. In contrast, for the CFRP body, Definition 1 provided an equivalent level of protection in the ICNIRP guidelines. However, Definitions 1 and 2 did not meet the requirements of the IEEE standard, whereas Definition 3 met this requirement.