## 2 Materials and Methods
### Magnetic Field and RF-EMF Data Acquisition
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Band Number** & **Technology** & **Frequency (MHz)** \\ \hline
1 & FM & 87–107 \\
2 & TV3 & 174–223 \\
3 & TETRA I & 380–400 \\
4 & TV445 & 470–615 \\
5 & B28 (UL) & 703–748 \\
6 & B28 (DL) & 758–803 \\
7 & LTE 800 (DL) & 791–821 \\
8 & LTE 800 (UL) & 832–862 \\
9 & GSM + UMTS 900 (UL) & 880–915 \\
10 & GSM + UMTS 900 (DL) & 925–960 \\
11 & GSM 1800 (UL) & 1710–1785 \\
12 & GSM 1800 (DL) & 1805–1880 \\
13 & DECT & 1880–1900 \\
14 & UMTS 2100 (UL) & 1920–1980 \\
15 & UMTS 2100 (DL) & 2110–2170 \\
16 & B40 TDD & 2300–2400 \\
17 & WIFI 2G & 2400–2483 \\
18 & LTE 2600 (UL) & 2500–2570 \\
19 & LTE 2600 (DL) & 2620–2690 \\
20 & WIFI 5G & 5150–5850 \\ \hline \hline \end{tabular} DL: Downlink; UL: Uplink.  
\end{table} 
Table 2: Measured frequency bands of the EME Spy Evolution PEM. Figure 5: An image of a measurement being taken with the EME SPY inside an electric bus. Twenty channels of band-selective RF-EMF, recorded at 6 s intervals for 120 min, were used in the analyses using EME SPY in this study. The exposure levels in RMS are collected from 20 different RF-EMF frequency bands, and the total RF-EMF is referred to as the sum of all frequency bands. The total E (E\({}_{\text{T,r}}\)) level at rth sample in the environment is calculated using Equation (1) for band-selective RF-EMF measurements. E\({}_{\text{i,r}}\) is the electric field strength for the ith band of rth sample, and N refers to the frequency spectrum's total number of bands (the value of N is 20). \[\text{E}_{\text{T,r}}=\sqrt{\sum_{i=1}^{\text{N}}\left(\text{E}_{\text{i,r}} \right)^{2}} \tag{1}\]  
For given ith band, the resulting isotropic E field strength of the three directions (E\({}_{\text{i,r,x}}\), E\({}_{\text{i,r,y}}\), and E\({}_{\text{i,r,z}}\) are the electric fields measured in the x, y, and z directions of rth sample) can be expressed as follows (2):  
\[\text{E}_{\text{i,r}}=\sqrt{\left|\text{E}_{\text{i,r,r}}\right|^{2}+\left| \text{E}_{\text{i,r,r}}\right|^{2}+\left|\text{E}_{\text{i,z,r}}\right|^{2}} \tag{2}\]  
We are considering a six-minute average according to ICNIRP's guidelines. The time-averaged electric field strength (E\({}_{\text{T,avg}}\)) is calculated as follows (3):  
\[\text{E}_{\text{T,avg}}=\sqrt{\frac{\sum_{r=1}^{\text{R}}\left(\text{E}_{ \text{T,r}}\right)}{\text{R}}} \tag{3}\]  
where R denotes the total number of samples in a time window for an average RF-EMF value. For example, in the case of 6 min, value of R is 60 considering data are taken every 6 s. The contribution of the predominant bands to the total E is calculated using (4) as follows:  
\[\text{P}_{\text{r}}=\frac{\text{E}_{\text{i,r}}^{2}}{\text{E}_{\text{T,r}}^{ 2}}\times 100 \tag{4}\]  
\(\text{P}_{\text{r}}\) shows the percentage of a band (E\({}_{\text{i,r}}\)) relative to the total E.  
This study analyzed all data using an Intel Core i7-12650H 2.30 GHz, 16.0 GB RAM computer, and MATLAB version 2022b. For RF-EMF measurements, each RF-EMF value was recorded at three different locations on each bus across two different bus routes during morning and evening hours and was analyzed using MATLAB software, version 2022b. The total RF-EMF values and band selective RF-EMF values were extracted from the data for analysis. Using these values, the variation in RF-EMF during the measurement period, box plots, and the contribution of each band to the total RF-EMF were analyzed. Additionally, using the GPS data and total RF-EMF values recorded during the measurements, the data were mapped and visualized with the help of ArcGIS software, version 10.1. Similarly, B measurements were performed at the same locations and times as the RF-EMF measurements, resulting in a total of six sets of measurement data. Using these values, the variation in B during the measurement period, box plots, and statistical analyses of B measurements were conducted. The B values were also mapped and visualized.