## 3 Results and Discussion
### Electromagnetic Field on Different European Roads
#### 3.1.7 The Republic of Serbia
The obtained results also show that in a very dense urban area, the electric field values are higher compared to rural ones. These observations are also confirmed by the results of other authors [38]. Analyzing the data from all measurements, we see that the mean and median of the E-field on the \(y\)-axis of LSProbe are slightly higher for the road sections presented in Figures 3-6, 9-11, 13, 14 and 16-24 compared to the E-field values on the other two axes. These results are due to the complex environment in which the electromagnetic waves propagate in the car cabin. The electric field measured by the LSProbe is a combination of both signals penetrated through windows and reflected off the inside of the vehicle body. When electromagnetic waves reflect off car interior surfaces, their polarization is changed. The fact that the E-field on the \(y\)-axis is slightly higher means that electromagnetic waves penetrating through the car side windows fall on the \(y\)-axis (placed parallel to the side windows). Electromagnetic waves that penetrate through the other car windows are reflected off interior surfaces and fall over on the antenna. These results may be applicable in the development of new materials for car interiors that have excellent electromagnetic wave absorption properties [39] and thus lead to a reduction of both passenger exposure and electromagnetic interference. The results will also apply to EMF energy harvesting,  
Figure 25: The Republic of Serbia: (**a**) Boxplot showing total electric field (\(E_{total}\)) and electric field on each axis (\(E_{x}\), \(E_{y}\), and \(E_{z}\)). The central dotted line in the box shows the median, and the bottom and top edges are the 25 th and 75 th percentiles, respectively; (**b**) Map showing the selected road on which measurements were taken. helping to more precisely determine the locations of the rectennas so that more EMF energy can be harvested in the vehicle during travel. From the data, we can see that higher maximal values of the electric field are observed in the car cabin when driving on roads that pass through large cities or ring roads of large cities. In Figure 26, a comparison between the different road sections is made. We see from Figure 26a that the distributions of \(E_{total}\) in the car's cabin during driving on the road sectors P1 AT-P2 AT and P6 RS-P7 RS have a higher median line than others. Moreover, the P1 AT-P2 AT and P6 RS-P7 RS medians are higher than the upper quartile for P3 BG-P4 BG, P2 HR-P3 HR, P2 HU-P3 HU, P2 IT-P3 IT, and P2 SI-P3 SI. Hence, we can conclude that the entire distributions of \(E_{total}\) on P1 AT-P2 AT and P6 RS-P7 RS are shifted upwards relative to other road sectors. From the data in Figure 26b, we see that the lower quartile and median are about the same for the distributions of \(E_{total}\) in the car's cabin during driving on the road sectors from motorways or roads through small cities and villages: P1 HR-P2 HR, P1 HU-P2 HU, P3 IT-P4 IT, and P4 RS-P5 RS. In addition, the median for the distributions in P2 AT-P3 AT and P1 SI-P2 SI is higher than the median for P1 HR-P2 HR, P1 HU-P2 HU, P3 IT-P4 IT, and P4 RS-P5 RS. In [8], after analyzing data from five large monitoring networks for different microenvironments in five European countries, the authors conclude that electric field values increase with increasing population density. The obtained results in this work also show that in urban and suburban environments, the electric field values are higher compared to rural ones.