Travel preferences of public transport users under uneven headways

Abstract

Public transport is affected by different types of randomness which impact the reliability they offer. The source of this randomness may come, for example, from casual uncertainty sources, such as accidents or protests, or from systematic uncertainty, related to service supply, such as dwelling time or travel time between consecutive stops. In addition to these sources of variability, an extra source of uncertainty experienced by users arises due to the public transport vehicle not being immediately available to avoid a wait of uncertain length. In a frequency-based system (without schedules), even under perfect regularity, users are not sure about the next vehicle’s time of arrival. This article aims to find out the impact that reliability has on travellers’ public transport alternative choice. To do so, an experiment of stated preferences is carried out, where the design characteristics are four operational attributes: speed, frequency, headway regularity, and average demand. Every scenario is randomly generated, based on the operational characteristics of the specific scenario. This means the alternatives presented resemble real-life operation and they are different between respondents. A Hybrid Discrete Choice Model was estimated, which addresses preference heterogeneity by considering two latent attitudes: punctual behaviour and crowding aversion. Overall, results indicate that headway irregularity has a significant effect on travellers’ choices, both in terms of waiting time and passenger density. This confirms this attribute should not be ignored in any public transport model, especially when it comes to evaluate projects which improve the system’s reliability but not necessary its average level of service.