Re-estimating UK Appraisal Values for Non-work Travel time Savings Using Random Coefficient Logit Model

Abstract

The official appraisal values of travel time savings (VTTS) for non-work trips in UK were estimated by basic discrete choice model on stated choice data collected over 20 years ago. This choice model developed by Bates and Whalen (2001) was specified to address some long-standing issues in the field of VTTS valuation including the sign and size of VTTS while allowing continuous interactions between VTTS and journey covariates. With respect to the size issue, it was found that a "tapering" function, whereby time changes are increasingly discounted, could best explain the lower unit utility observed for small time savings (STS). While this set of non-work VTTS is still being used for transport appraisal in UK, the field of discrete choice modelling has evolved significantly brought by a leap of computing power and improved simulation techniques. Notably, advanced model such as mixed multinomial logit (MMNL) has been widely used to facilitate more realistic travel behavioural modelling by explaining random taste heterogeneity across respondents, which cannot be achieved in a deterministic manner. Also, techniques in specifying such model for VTTS valuation are well established by researchers nowadays. The key objective of this research was then to apply the MMNL model and re-estimate the current UK VTTS within a random coefficient logit framework. Alongside the theoretical discussions, this paper presents a synthesis of empirical evidence to support an updated appraisal value for non-work travel time savings in UK. Some key findings from this paper include a much higher mean value for the VTTS and the significantly reduced "perception effect" for the STS. In particular, this research found that MMNL model substantially reduces the "tapering" parameter of the discounting function for STS such that the "perception effect" of the VTTS becomes minimal. This finding suggests that travel benefits due to STS should be included for transport appraisal and it challenges some appraisal frameworks for countries like Germany where VTTS are discounted or even completely ignored for STS.

Using a sequential latent class approach for model averaging: Benefits in forecasting and behavioural insights

“…The first is to apply model averaging across multiple candidate models that all have advantages and disadvantages, where there is no clear cut case for choosing which is best. One obvious example of this is in the choice of distribution(s) within mixed logit models (Guo and Wilson, 2007;Hess, 2010;Tjiong, 2015). A second and rather different context in which the benefits of implementing model averaging are clear is in the case of very large-scale applications, either with large datasets or large choice sets.…”

Analytical Model for the Change of Travel Time Savings With Waiting Time and Service Level

“…Considering the importance of the value of travel time savings in transport project appraisals, its theory frameworks have been widely applied in practical empirical studies. Various discrete choice models, including mixed logit [16]- [22], multinomial logit [23]- [29], binary logit [30], [31], nested logit [32]- [34] models, have been widely used to investigate the influence of variables in the empirical analysis. Hess et al [16] estimated the value of travel-time savings via mixed logit models to analyze the effects of random taste heterogeneity.…”

“…Hensher [19] derived the values of travel time savings using mixed logit models and found that less-restrictive choice model specifications tend to produce high estimates of values of time savings. Tjiong [22] re-estimated the values of travel time savings for nonworking trips presented using a mixed logit model. Cirillo and Axhausen [23] presented the results of a multinomial logit model, focusing on the distribution of the values of travel time savings.…”