Abstract
There is a strong interest among policy makers in measures intended to rationalize private car use. However, this requires prior assessment of the likely impact on car and public transport demand associated with each policy option. For example, what is the likely effect of a reduction of travel time by public transport on mode choice? Such effects can be quantified as elasticities, defining the percentage change in a response variable to a 1% change in an independent variable. The aim of this study is to provide a quantitative overview of the impact of travel time, its components, and its derivatives on transit demand. Data were used from a Belgian mobility survey that was supplemented with a database with a calculated public transport trip for each trip in the mobility survey, with the use of search engines and timetables from the public transport companies. Various functional models were applied to derive demand elasticities. An evaluation of these calculated travel times with public transport search engines shows considerable but reasonable differences with observed trips. Travel time ratios, comparing car and transit travel times, and generalized time estimations, weighting walking and waiting times, offer the best approach to identify the relation between travel time and transit use and result in strongly negative elasticities, particularly when captive travelers are separated. The study contributes to the discussion on the effect of travel time on public transport demand not by using a transport model but by using a survey and transit timetable information.
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