Contents lists available at ScienceDirect Transportation Research Part A journal homepage: www.elsevier.com/locate/tra Noise, odor and passenger density in perceived crowding in public transport Bin Wang, John Zacharias ⁎ Laboratory for Urban Process Modelling and Applications, Peking University, Beijing, PR China ARTICLEINFO Keywords: Travel comfort Subway Crowding Ambient environment ABSTRACT Public transport is being promoted worldwide to help resolve the environmental and congestion problems besetting cities. Travel comfort is increasingly seen as crucial to effecting the switch from private motorized modes to public transit. The purpose of this study is to measure the physical and human factors impacting travel comfort on mass urban rail transport. Randomly selected passengers (n = 368) commuting in subway cars at 14 levels of in-vehicle passenger density were intercepted to evaluate their satisfaction with the following factors related to comfort: crowding, noise, smell, air quality, temperature, illumination, vibration and safety from crime. Satisfaction with regard to crowding was negatively and linearly related to the number of passengers in the subway car. In the multiple regression model, however, perceived noise in- tensity accounted for more than the actual number of individuals in the car in the evaluation of crowding, with smell as a second significant contributor. Other significant factors in travel comfort included air quality, temperature, and fear of crime. Although it is found that objectively measured passenger crowding explains a major part of perceived travel comfort, other factors associated with the ambient environment are at least as important. Corrective measures to im- prove travel comfort could address the ambient environmental factors in the medium term, while the structural issue of over-crowding needs to be addressed in the longer term. 1. Introduction 1.1. The importance of travel comfort in effecting the switch to public transport As incomes rise, demand for improvement in personal wellbeing increases (Shafik, 1994), that extends to the daily life of travel in the public environment. In most surveys comparing the comfort and desirability of various forms of transport within cities, public transport ranks rather lower than private modes, including the bicycle. Lancée et al. (2017) showed that commutes by bicycle or on foot in the Netherlands led to greater travel satisfaction than commutes by motorized modes, regardless of distance. Friman et al. (2013) uncovered the same response in Sweden, while Smith (2017) also demonstrated the active transport advantage in Portland, Oregon, USA. In Shanghai, all travel on a bicycle, regardless of purpose, was perceived as more comfortable than by public transport, with the bus being seen as particularly uncomfortable (Zacharias, 2002). At least for walking and by extension for the bicycle as well, the controlled interaction with the social environment and natural features along the route enhances feelings of satisfaction (Ettema & Smajic, 2014). Self-selection of travel mode is a possible problem with these cross-sectional studies since those biking or walking might like to do so while those driving might not like active travel. Martin et al. (2014) addressed this problem to some extent by https://doi.org/10.1016/j.tra.2020.03.013 Received 30 April 2019; Received in revised form 24 February 2020; Accepted 9 March 2020 ⁎ Corresponding author. E-mail address: johnzacharias@pku.edu.cn (J. Zacharias). Transportation Research Part A 135 (2020) 215–223 Available online 20 March 2020 0965-8564/ © 2020 Elsevier Ltd. All rights reserved. T