## 3 Results  
The driving distance in each prefecture is described in Table 3, together with the average driving speed and two coverage ratios, as described below. We used the reference area mesh provided by the Japanese government [31] to divide the measurement area into a 1 km\({}^{2}\) mesh. Information such as population density is linked to this mesh so that we can estimate how many people live in the area mesh we measured. The population coverages are shown in Table 3 as the ratio of the population summed over the meshes through which the car was driven to the total population in each prefecture. The mesh area coverage is the ratio of the measured number of meshes with the number of meshes in the prefecture assumed to be 100%. The mesh area coverage is low, but the population coverage is high. This is related to the existence of places where cars are not driven, such as mountains, rivers, and narrow roads. \begin{table}
\begin{tabular}{c c c} \hline
**Prefecture** & **Area [km\({}^{2}\)]** & **Population [k]** \\ \hline Tokyo & 2104 & 14,048 \\ Kanagawa & 2416 & 9237 \\ Saitama & 3768 & 7345 \\ Chiba & 5082 & 6284 \\ Ibaraki & 6096 & 2867 \\ Tochigi & 6408 & 1933 \\ Gunma & 6362 & 1939 \\ Shizuoka & 7255 & 3633 \\ Yamanashi & 4201 & 810 \\ \hline \end{tabular}
\end{table} 
Table 2: Area and population of each prefecture in 2020. Figure 3: Radius of 100 km centering on Nihonbashi, Tokyo, and scene of measurement in front of Mt. Fuji (inset). Figure 4a shows the E-field strength distribution in the whole band for the measurement results in Tokyo as an example. The E-field strength at each measurement point is indicated by a colored circle. It can be seen that there is a difference in the E-field strength between the center of Tokyo and the suburbs. In particular, in the enlarged view around Nihonbashi shown in Figure 4b, the E-field strength is more than 110 dB\(\mu\)V/m in most cases, whereas it is less than 110 dB\(\mu\)V/m in rural areas (Figure 4c). Figure 5 shows the box plot of the E-field strength from mobile phone base stations, including 5G (a) and only 5G (b) and broadcast transmission towers of FM (c) and TV (d) with the number of samples for each prefecture. The E-field strengths in the graphs are levels averaged within the reference area mesh (1 km\({}^{2}\) mesh) [31]. Note that 5G in Yamanashi is omitted because the number of samples is only six. It can be seen that the E-field strengths of FM/TV broadcast transmission towers (Figure 5c,d) are lower than that of mobile phone base stations (Figure 5a). It is also clear that the E-field strength of only 5G mobile phone base stations (Figure 5b) is approximately 20-30 dB lower than that of all mobile phone systems (Figure 5a). It has been reported that the E-field strength and its frequency from the 5G mobile phone base station varies depending on the data traffic [32]. In particular, when the downlink traffic increases, the time occupancy of the downlink signal may increase. In this measurement, the communications by terminals were not performed in the car. It is expected that the time-averaged E-field strength will be much higher than the above results when data traffic, especially downlink, exists. The E-field strength of all bands is higher in Tokyo than in other prefectures. The E-field strengths of mobile phone base stations and FM bands in Kanagawa and Saitama prefectures follow those of Tokyo. There is no clear trend in the E-field strength of TV except for Tokyo, which seems to be affected by the location of transmission towers. There are the Tokyo Skytree and the Tokyo tower, which are both broadcast transmission towers in the center of Tokyo, but also covering other prefectures described in Table 2, except for Yamanashi. The E-field strength of TV is relatively high in Yamanashi Prefecture because most of the measurement routes are near broadcast transmission towers.