Tollroads are only part of the overall trip: the error of our ways in past willingness to pay studies

Abstract

With rare exception, actual tollroad traffic in many countries has failed to reproduce forecast traffic levels, regardless of whether the assessment is made after an initial year of operation or as long as ten years after opening. Pundits have offered many reasons for this divergence, including optimism bias, strategic misrepresentation, the promise to equity investors of early returns on investment, errors in land use forecasts, and specific assumptions underlying the traffic assignment models used to develop traffic forecasts. One such assumption is the selection of a behaviourally meaningful value of travel time savings (VTTS) for use in a generalised cost or generalised time user benefit expression that is the main behavioural feature of the traffic assignment (route choice) model. Numerous empirical studies using stated choice experiments have designed choice sets of alternatives as if users choose a tolled route or a free route under the (implied) assumption that the tolled route is tolled for the entire trip. Reality is often very different, with a high incidence of use of a non-tolled road leading into and connecting out of a tolled link. In this paper we recognise this feature of route choice and redesign the stated choice experiment to account for it. Furthermore, this study is a follow up to a previous study undertaken before a new toll road was in place, and it benefits from real exposure to the new toll road. We find that the VTTS is noticeably reduced, and if the VTTS is a significant contributing influence on errors on traffic forecasts, then the lower estimates make sense behaviourally.Key words: value of travel time savings, toll routes, free routes, choice experiment, errors in forecasts Acknowledgment. We thank the three referees for their comments as well as Stephane Hess who have provided invaluable comments which have resulted in numerous improvements to the paper.

Modelling effects of changes in travel time and costs of toll road usage on choices for residential location, route and travel mode across population segments in the Jakarta-Bandung region, Indonesia

“…Furthermore, it is also relevant to estimate marginal willingness to pay (WTP), as the measure of the value of travel time savings (VTTS), as plays a crucial role in economic evaluation of transport projects and in pricing policies. It describes how much the travel cost attribute is required to change given a one unit change of travel time attribute, such that the change in total utility will be zero (Rose and Hensher, 2014). The marginal WTP is defined by the ratio of the derivatives of travel time and costs, assuming a linear utility function and therefore the value is constant across individuals.…”

Estimation of Value of Travel Time in Trinidad and Tobago

“…Therefore, travellers erroneously think that the delay faced on the entire trip will be eliminated and not only for the section where the new toll facility will be implemented [7]. It can be argued that in most SP studies the trade-off between money and time is assumed to occur over the entire trip, including free roads that lead to the tolled facility [23].…”

“…The number of attribute levels was limited to three to ensure that there were not too many discrete choice games. The length of the survey was kept to a minimum since respondents can get fatigued if there are too many questions [23]. The cost per hour values that varied from $6.67 per hour to $120 per hour, resulting in a range in which the median was sufficiently close to the previously determined baseline value of $53.38 obtained from the wage rate.…”

Full-Scale Controlled Comparison of Alternative Information Formats for Stated Choice Exercises

“…In both stated choice exercises, a distinction was made between time on an expressway and time on other roads following the recommendations of a recent study that investigated why the forecast levels of traffic had failed to materialize on many newly constructed toll roads (16). Overall, the route choice exercise was by far the simpler of the two, with respondents having to consider just 4 attributes compared with 15 in the mode choice exercise.…”