## 1 Introduction  
Rolling stock, a crucial part of railway transportation systems with a limited operational lifespan, requires replacement to keep services efficient. Within today's budget constraints, railroad and transit operators inevitably face decisions on the most suitable equipment for specific services. This raises questions about what equipment is best suited to replace existing ones, and various agencies and operators employ diverse metrics to determine the optimal rolling stock configurations [1]. In the realm of rolling stock performance, it is widely acknowledged that passengers prioritize clean, comfortable vehicles that facilitate easy boarding and alighting. The challenge lies in determining the relative importance of these factors, including comfort level. Estimating the effects of improving rolling stock on ride quality is possible by relating these improvements to fares and In-Vehicle Time (IVT) metrics. Improved ride quality can increase passenger satisfaction, which may result in higher ridership levels or longer journey times [2, 3]. For example, if a 10% improvement in passenger satisfaction leads to a 2% increase in ridership or a 5% decrease in the perceived In-Vehicle Time (IVT), this could be used to estimate the impact on fare revenue or operational costs. Transportation planning also faces environmental challenges, particularly in terms of noise and vibration associated with railways. Vibrations originating at the vehicle-track interface can affect passengers and infrastructure, contributing to structural noise. Vibrations can cause fatigue, muscle strain, headaches, dizziness, nausea, and other health issues when experienced for extended periods or at high intensities [4, 5]. In railway environments, vibrations are generated by train movement on tracks, track irregularities, wheel-rail interaction forces, and pantograph-catenary interaction [6, 7]. The discomfort caused by vibration is influenced by frequency content (low frequencies generally cause more discomfort), amplitude, duration, and pattern. Additionally, vibrations within the track can accelerate wear on components such as sleepers, pads, and fastenings. Noise exposure can lead to temporary or permanent hearing loss, sleep disturbances, stress, anxiety, and other adverse health effects [4; 5]. In railway environments, noise sources include rolling stock engines, wheelsets, brakes, air conditioning systems, passenger interactions, track-borne noise (e.g., rail joint clatter), pantograph-catenary interaction, and structure-borne vibration transmission from the train to its surroundings. The discomfort caused by noise is influenced by factors such as sound pressure level, frequency content, duration, and pattern. The combined effect of vibration and noise on comfort can be assessed using subjective measures like annoyance ratings or objective physiological responses (e.g., heart rate variability). Several studies have investigated the relationship between these two factors in various transportation contexts, including railways. These investigations often involve controlled laboratory experiments where participants are exposed to different vibration and noise levels while completing tasks related to their comfort perception or performance under such conditions [8]. Examining the specific case of the Warsaw metro, we analyzed vibrations and noise across various metro train types, ranging from older models to the most modern ones (Figure 1). The evaluation analyses vibration and noise levels at different positions within each train's interior. The goal is to identify trends in vibroacoustics and assess how each type performs in terms of generating, transmitting, and mitigating vibrations. While there have been extensive studies on vibroacoustic phenomena in railways, there is still a gap in understanding how these factors collectively influence overall passenger comfort. Additionally, there is a need for convenient rating scales to compare different train types.