Nonlinear effects of bus micro-environments on passengers’comfort

Abstract

Buses play an important role in the daily travel of urban residents. Bus micro-environmental pollution and its adverse impacts on passengers' physical and psychological well-being has become an increasing concern among the general public, researchers, and policymakers. However, few studies have examined the nonlinear effects of bus micro- environments on passengers' comfort, analyzed the threshold values of multiple microenvironmental variables, and ascertained the optimal micro-environmental exposure levels for passengers. In this study, real-time monitoring data of bus micro-environments, questionnaire survey data of 520 passengers, travel characteristics, and environments outside the buses were simultaneously collected on six bus routes in Guangzhou City. Nonlinear regression models constructed by random forest were then employed to explore the relationships between bus micro- environments and passengers' comfort. The results show that in- bus temperature, relative humidity, PM2.5 concentrations, noise, and passenger load have nonlinear effects on the comfort, but the importance and mechanism of each micro- environmental variable in influencing comfort is different. Passengers have a higher degree of comfort when in- bus temperature is 23.5- 28.0 ℃, relative humidity is 45%-58%, PM2.5 concentrations are lower than 28 μg/m³, noise level is lower than 75 dB, and passenger load is 8- 26 persons. Also, there are some differences between the optimal micro- environmental exposure levels identified in this study and current environmental standards. These findings have theoretical and practical implications for policymakers, transportation planners, and bus operators when improving bus microenvironments and promoting passengers' comfort.