# Impact of Environmental Factors on Passenger Ride Comfort
## 7 Results of Experimental Studies  
### Vibration Comfort Results  
Figures 8-10 present the results of the RMS values of the longitudinal vibration accelerations in the one-third octave bands. These values were calculated on the basis of measurements carried out on the passenger seat of a medium-class passenger car on two classes of roads differing in their state of maintenance. All the measurements presented were recorded on straight road sections. vibrations with low-frequency one-third octave bands on the main road with better pavement quality do the RMS accelerations have higher values than those recorded on the local road surface. Temporal signals of vibrations were also recorded in metro cars of two different types, i.e., a Skoda Varsovia metro car (new trains) and a Russian-made car of type 81-572P (old trains). Figures 11-13 show the RMS values of vibration acceleration in the one-third octave bands for the three vibration directions. At this point, it should be noted that the position of the human body in these vehicles differs from the position occupied in a passenger car. A passenger seated in a metro car is oriented transversely to the direction of vehicle motion. The measurements were therefore defined with respect to the human body in the standard ISO 2631:1. Accordingly, the x-axis, corresponding to longitudinal vibrations, is oriented transversely to the direction of vehicle motion, and the y-axis (for transverse vibrations) is along this direction. Figure 11: RMS values of longitudinal vibration accelerations in one-third octave bands measured in Skoda Varsovia (new train) and type 81-572P metro cars (old train). Figure 12: RMS values of transverse vibration accelerations in one-third octave bands measured in Skoda Varsovia (new train) and type 81-572P metro cars (old train). Figure 13: RMS values of vertical vibration accelerations in one-third octave bands measured in Skoda Varsovia (new trains) and type 81-572P metro cars (old trains). The results recorded in the metro trains indicate worse conditions of vibrational comfort in the older trains, especially in the context of vertical vibrations. The values of vibration accelerations recorded in the car are significantly higher compared to those measured in the metro trains. The RMS values in one-third octave bands, calculated from the measured vibration accelerations, are averaged with Equation (2) using the relevant weights from the ISO 2631-1 standard for each of the vibration directions. The synthetic index of vibrational comfort \(a_{w}\) is then determined with Equation (3) and related to the C1 scale.. The weighted acceleration values and synthetic indices are shown in Table 9.  
In this study, the synthetic vibration comfort index \(a_{w}\), defined by Equation (3) as the total weighted RMS acceleration, indicates a comfort level of 5 (\"very comfortable\") for the new metro train and a slightly reduced comfort level, though still rated 5, for the older metro train. This suggests that even though older cars exhibit higher vibration accelerations, they remain within the threshold for a comfortable experience according to the ISO 2631-1 standard. In contrast, the Montreal study [30] utilised the vibration index defined in the ISO 2631-4 standard [51] and focused on percentile-based metrics for a number of short (5 s) time intervals (95 th percentile). While specific vibration index values are not directly comparable due to differing methodologies, the overall findings align: newer metro cars consistently deliver superior vibration comfort compared to older ones. Moreover, the Montreal study highlights greater stability in vibration comfort indices along routes with varying vehicle speeds, suggesting that newer cars are better equipped to manage fluctuations caused by track conditions and speed variations. These nuances in the Montreal study provide insights into operational factors that were not explicitly considered in the present analysis, in which vibration accelerations are averaged across a whole journey.