# Impact of Environmental Factors on Passenger Ride Comfort
## 7 Results of Experimental Studies
### Ride Comfort Index  
Table 13 summarises the results of the comfort ratings for the four types of comfort: vibrational, acoustic, thermal, and visual. These ratings have been developed on the basis of the measurements carried out, taking into account the adopted comfort scales. Each type of comfort and the respective comfort index Ci (i = 1, 2, 3, 4) correspond to different aspects of passenger comfort: vibratory comfort refers to the perceived mechanical vibrations, acoustic comfort refers to the noise level, thermal comfort takes into account the temperature and relative humidity of the air, and visual comfort analyses the intensity of lighting. According to the proposed evaluation method, based on the levels C1, C2, C3, and C4 of different types of comfort, the value of the index C describing the overall ride comfort was assigned to each of the means of transport studied. In addition, the secondary comfort index \(N_{C}\) and the expanded index \(C_{exp}\) of overall comfort were calculated to enable comparisons between journeys with the same values for the primary index C. Table 13 presents the relevant results for different types of comfort, including both partial and overall comfort indices. The highest level of vibrational comfort was achieved in the passenger car on the main-class road and both metro trains. The car on the local road scored slightly lower (C1 = 4), which can be attributed to the poorer quality of the road surface, characterised by unevenness, potholes, and insufficient maintenance. The discrepancy in vibrational comfort between the main-class and local roads highlights the crucial role of road quality in determining ride comfort. On the main-class road, smoother pavement with minimal imperfections likely facilitated a stable and uniform ride, reducing oscillations transmitted to the vehicle. In contrast, the local road's degraded surface likely amplified vibrations, particularly at lower speeds or when traversing uneven sections. For metro trains, the consistency in comfort levels in both types of trainsets suggests that factors like rail track maintenance and suspension systems effectively mitigate vibrational disturbances. This consistency could also be influenced by the isolated and controlled environment of metro tunnels, shielding them from external disruptions such as weather or traffic-induced vibrations. Thermal comfort on metro trains differs between new and old trainsets--the new trainset achieves a higher thermal comfort level (C3 = 4) compared to the older trainset, which scored (C3 = 3), suggesting better control of temperature and internal conditions in the newer rolling stock. The lower thermal comfort ratings in the older metro trainsets may stem from outdated HVAC (heating, ventilation, and air conditioning) technology, limited insulation, or poor circulation. For the passenger car, thermal comfort was rated at C3 = 3, attributed to the high air temperature of 28 \({}^{\circ}\)C during the test period (summer season). This elevated outside temperature likely strained the car's air-conditioning system, leading to suboptimal cooling and a diminished comfort level. The difference between the thermal \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Vehicle**} & \multirow{2}{*}{**Vibrational C1**} & \multirow{2}{*}{**Acoustic C2**} & \multirow{2}{*}{**Thermal C3**} & \multirow{2}{*}{**Visual C4**} & \multicolumn{2}{c}{**Overall Comfort Index**} \\ \cline{5-6}  & & & & & & C (\(N_{C}\)) & \(C_{exp}\) \\ \hline Car, main road & 5 & 4 & 3 & 5 & 3 (1) & 3.455 \\ \hline Car, local road & 4 & 2 & 3 & 5 & 2 (1) & 2.345 \\ \hline Metro, new train & 5 & 3 & 4 & 5 & 3 (1) & 3.455 \\ \hline Metro, old train & 5 & 2 & 3 & 4 & 2 (1) & 2.345 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Comfort indices Ci (i = 1, 2, 3, 4) of different types of comfort, overall ride comfort index, C, its secondary index \(N_{C}\), and expanded index \(C_{exp}\) of overall ride comfort for passenger car and metro trains.