# Impact of Environmental Factors on Passenger Ride Comfort
## 4 Methodology
### Thermal Comfort  
Thermal comfort depends on individual factors and environmental conditions. The former include metabolism, physical activity, the ability to acclimise, or the thermal insulation of clothing. In the second group are air temperature, the relative humidity and air flow velocity, surface radiation temperature, and the asymmetry of temperature distribution in the room. Most individual and environmental factors are taken into account when determining the PMV (Predicted Mean Vote) index. This index assesses the average thermal sensation of a group of people indoors on a 7-point scale from \(-3\) (too cold) to \(+3\) (too warm). The same factors are taken into account when determining the related PPD (Predicted Percentage of Dissatisfied). This index is used to determine the percentage of people who are likely to be dissatisfied with the thermal environment. The higher the PPD value, the more likely  
Figure 4: Proposed scale of acoustic comfort index C2 with five levels (1 to 5) defined in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Standard** & \
\begin{tabular}{c} **Recommended Equivalent Sound Level** \\ **LAeq [dB(A)]** \\ \end{tabular} &
\begin{tabular}{c} **Additional Information** \\ \end{tabular} \\ \hline \multirow{4}{*}{UIC 660} & Middle of the carriage: max. 65 dB(A) & Permissible levels for rail vehicles at a maximum speed of 250 km/h, \\  & Between carriages: 75 dB(A) & outside of tunnels \\  & Middle of the carriage: max. 73 dB(A) & Permissible levels for rail vehicles at a maximum speed of 250 km/h, \\  & Between carriages: 82 dB(A) & in tunnels \\  & Max. 70 dB(A) & Acceptable level for health with 24 h exposure \\  & Max. 75 dB(A) & Acceptable level for health with eight-hour exposure \\ \cline{1-1}  & \textgreater{}55 dB(A) & Noise level highly annoying to few people during daytime \\ \cline{1-1}  & \textgreater{}50 dB(A) & Noise level moderately annoying to few people during daytime \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Noise recommendations of standards and institutions. people are to be dissatisfied with the thermal conditions. Both indices were developed by [PERSON] [38] and remain a recognised standard for assessing thermal comfort in the ISO 7730:2012 standard [39]. The determination of these indices, however, is resource-intensive in the form of time-consuming measurements and the involvement of complex measuring apparatus. Consequently, it may not be practical to use this method to assess thermal comfort in vehicles, especially for short journeys, where simpler methods can provide sufficient information on such comfort. The Central Institute for Labour Protection--National Research Institute (CIOP), which is a state research institute in Poland, considers a temperature in the range of 23 \({}^{\circ}\)C to 26 \({}^{\circ}\)C to be optimal for thermal comfort in office spaces [40]. This range refers to conditions in which a person at rest is dressed in light clothing and the humidity is equal to 50%, while at the same time, the temperature of the walls and air is the same. It should be noted that the effect of humidity on thermal comfort, according to CIOP, is much greater at high temperatures. Higher humidity intensifies the thermal sensations, while too low humidity causes discomfort due to drying of the skin or mucous membranes. For optimal health conditions, a humidity of between 40% and 70% is recommended. Similar recommendations are formulated in the already cited ISO 7730:2012 standard, distinguishing between temperature ranges for the winter season (20 \({}^{\circ}\)C to 24 \({}^{\circ}\)C) and summer season (23\({}^{\circ}\)C to 26\({}^{\circ}\)C). Requirements for thermal comfort parameters with direct application to means of transport are formulated in the standards EN 14750-1:2006 [41] and UIC 553:2004 [42]. The former, with reference to ISO 7730:2012, defines a more stringent temperature range of 19-22 \({}^{\circ}\)C in winter and 24-27 \({}^{\circ}\)C in summer. However, no humidity range is defined.