# Impact of Environmental Factors on Passenger Ride Comfort
## 3 Motivation and Purpose  
The current challenges of passenger transport, in addition to sustainability, also concern the increasing expectations and demands of passengers. Passengers' preferences most often included in the various indicators of the perceived quality level of transport services are a high level of safety, reliability, accessibility at the required place and time, and accessibility to information [6]. Ride comfort is also one of the important elements influencing the quality of these services. This issue is therefore becoming increasingly important in the context of competitiveness within different transport modes and carriers. Ride comfort can be a deciding factor between individual and collective modes of transport, especially in the context of daily, short-distance journeys. The importance of ride comfort is also increasingly recognised by researchers in the field of autonomous vehicles, who emphasise that enhancing comfort in these vehicles could play a pivotal role in encouraging broader public acceptance of this emerging technology [7]. A systematic survey and comprehensive assessment of ride comfort can therefore be a supportive tool for transport operators to react at an early stage to deviations from the desired level of service quality and to implement corrective solutions. The state of the art recognises the issue of comfort as an important one in the field of transport; however, the methods used so far to investigate and assess ride comfort are mainly limited to the selected factor affecting the passenger of the chosen means of transport. In this respect, the dominant factor taken into account is mechanical vibration, and various approaches to assessing vibration comfort have been proposed. An early study with a method of comfort assessment focused on mechanical vibrations was published in 1941 [8]. However, it defined comfort thresholds only within a limited frequency range of 1 to 12 Hz. This method was further developed by [PERSON], who introduced the Wz comfort index [9], which was widely used by European railways for an extended period. The Sperling index laid the foundation for subsequent normative documents, which are discussed in detail in Section 4.1. Current research on ride comfort is often based on the results of experimental tests carried out in vehicles during typical operation. Among other things, researchers have investigated the effects of the presence of obstacles in the form of speed bumps [10] and  
Figure 1: Ride comfort factors. changes in the suspension parameters of a rail vehicle on passenger comfort [11]. Simulation studies using quarter- and half-car models for road vehicles [12] and complex models for rail vehicles [13] have also been carried out. Another approach is the analysis of ride comfort based on laboratory tests on stands adapted to vibration excitation [14]. It is also common practice to compare experimental results with the subjective assessment of test groups [15; 16]. The assessment of ride comfort was also utilised in an innovative method for monitoring urban road surface quality, which leverages smartphone sensor technology and advanced computational methods [17]. A two-stage system was proposed: the first stage employs a CNN neural network with an MHA attention mechanism to quantify ride comfort based on vibrations, while the second stage uses a multi-source data fusion strategy to identify low-quality road segments. It should be noted that there is no unanimous approach to methods of evaluating ride comfort resulting from the effects of vibration on the passenger. Both experimental and simulation studies follow the recommendations of different standards and use different comfort indicators. Irrespective of the time of travel and the mode of transport, a number of different environmental factors affect humans simultaneously. Therefore, the assessment of ride comfort based solely on measurements or simulations of the effect of mechanical vibrations on the passenger seems to be insufficient for the currently increasing expectations of passengers.