# Impact of Environmental Factors on Passenger Ride Comfort
## 4 Methodology
### Visual Comfort  
According to the definition in the European standard EN 12665:2011 [43], visual comfort is the subjective feeling of visual well-being caused by the lighting environment. The lighting environment consists of natural light and artificial sources. The level of such comfort depends on a number of factors related to both the parameters of this environment and individual human preferences. Visual comfort is therefore influenced by the amount of light, its uniformity and colour, the risk of glare, and the ability of light to reproduce colours. The physiology of the human eye and human preferences are also important. To date, scientific research on this topic has mainly focused on the visual comfort of humans in closed spaces, particularly office spaces [44]. In the context of means of transport, the most important factor in terms of passenger visual comfort, and also safety, is illuminance, which is the ratio of the luminous flux incident on a plane to the surface area of that plane. The level of illuminance should ensure that the elements of space can be distinguished and simple visual tasks can be carried out comfortably. Too much or too little light can cause visual discomfort. The main document governing the lighting quality requirements for urban rail vehicles is the European standard EN 13272-2:2019 [45]. This standard defines the minimum requirements for lighting environment parameters such as glare, colour temperature, and colour rendering capacity. In addition, the document defines minimum illuminance levels in selected areas of the vehicle, such as seating areas, standing areas, or aisles. The Central Institute for Labour Protection--National Research Institute (CIOP) indicates that  
Figure 5: Proposed scale of index C3 for thermal comfort due to simultaneous effects of temperature and relative humidity in summer season, with five levels (1 to 5) defined in Table 1.  
regardless of the visual task being performed, an acceptable illuminance level is at least 200 lux [46]. On the other hand, the ISO 8995-1:2002 standard [47], which concerns lighting in workplaces, recommends a range of 300-700 lux for reading and writing tasks. Table 5 presents the lighting level recommendations from various standards and institutions. The proposed scale of visual comfort in terms of illuminance inside passenger compartments is based on the recommendations of the above-mentioned standards and institutions. The EN 13272-2:2019 standard recommends only minimum illuminance levels in carriages and is focused more on lighting quality than passenger comfort. No upper limit for illuminance is included in the standard. Its main objective is to provide comfortable lighting conditions for passengers who are engaged in visual work (reading, computer work) during the journey, but also for those who use the travel time for relaxation and rest. The authors propose that, due to the possible failure of luminaires and the varying perceptions and needs of passengers, further comfort levels should be limited for both minimum and maximum values. Although the ISO 9885-1:2002 standard refers to indoor workplaces, it recommends that a maximum illuminance level of 700 lx be considered as the limit for the comfort of any passenger. In addition, for reasons of passenger safety and health, a minimum illuminance level should be provided, particularly in emergency situations and during passenger exchanges. However, it cannot be assumed that the minimum values recommended for the above-mentioned reasons will also be appropriate in the context of ride comfort. Therefore, the range of all illuminance levels below the value of 200 lux, referred to as a minimum of level 5 (\"comfortable\") in the proposed scale, is divided into four smaller ranges. These ranges correspond to decreasing visual comfort and the respective levels from 2 to 5 on the proposed scale.