# Impact of Environmental Factors on Passenger Ride Comfort
## 4 Methodology
Accordingly, in the present paper, a common rating scale is developed for all factors based on guidelines from relevant international standards, which, however, do not directly provide such a consistent rating approach for each factor. This requirement also implies that factor-specific scales with a different number of levels for different factors, such as the ones defined in [30], are not suitable for direct application in the present method of comfort evaluation and need to be modified prior to their use. To refine the proposed approach, a secondary comfort index, \(N_{C}\), can be introduced to distinguish between the two situations where the main overall comfort index \(C\) is the same. For instance, if we consider two journeys, one with ratings of 5-4-3-5 and another with 3-3-3-3 ratings, while both journeys have the same overall comfort index \(C=3\), the first journey should be considered more comfortable. To quantify this preference, the secondary index \(N_{C}\) is defined for each journey as the number of factors with the lowest comfort rating, equal to the overall comfort index \(C\). The index \(N_{C}\) is then used only if the main index \(C\) is the same in different journeys. A higher value of \(N_{C}\) signifies a less comfortable journey, like in a journey with 3-3-3-3 ratings (\(N_{C}=4\)) compared to the 5-4-3-5 scenario (\(N_{C}=1\)). However, the index \(N_{C}\) itself may not always be sufficient to distinguish between different journeys with the same overall comfort score (index C). For instance, journeys A and B, with the respective ratings 3-4-5-4 and 3-4-4-4, have identical values for both \(C\) and \(N_{C}\). To address this issue, an expanded index \(C_{exp}\) of overall comfort can be introduced. This refined form of the \(C\) index is derived by sorting the individual comfort indices (C1, C2, C3, C4) in ascending order and then combining them into a four-digit number. The index \(C_{exp}\) is then obtained by inserting a decimal point after the first digit to maintain the same scale as for the individual indices. For the specific case of \(C=5\), corresponding to all individual comfort indices \(C_{i}\) at the highest level of 5, the expanded index \(C_{exp}\) is set to 5 in order not to go beyond the assumed scale. Using this approach, journey A with \(C_{exp}=3.445\) is rated higher than journey B with \(C_{exp}=3.334\), correctly reflecting the better overall comfort of journey A. As with the original index \(C\), the expanded form \(C_{exp}\) of the composite index of ride comfort is primarily designed to provide an overall assessment of ride comfort, not to pinpoint the specific factor contributing most to discomfort. Each of these overall indices is used in conjunction with the individual comfort indices, which provide detailed information on each aspect of comfort. Therefore, if a journey has a low overall comfort score (index C or \(C_{exp}\)), the individual indices \(C_{i}\) can be readily examined to identify the specific factor(s) responsible for the low rating. Due to the differences between the vehicles of the different modes of transport, their environments and the way they are operated, some comfort factors can be excluded from the assessment. For example, when travelling in a passenger car, passengers usually do not use interior lighting. The effect of daylight on visual comfort is also not taken into account. If any of the factors are excluded, their individual levels are assumed to be equal to 5. For each vehicle, specific factors were selected that, in the authors' opinion, may contribute to the passenger's assessment of the ride comfort level. In the case of the passenger car, vibration, thermal, and acoustic comfort were selected. Due to the different characteristics of the environment in which the passenger of the metro trains travels (tunnel travel), visual comfort was also included in the assessment of ride comfort in these vehicles.