Stated preference (SP) studies developed to estimate travellers' value of travel time savings (VTTS) on managed lanes (ML) may underestimate the VTTS. This study investigates survey design strategies and differentiating the VTTS for ordinary and six common urgent situations faced by the travellers in an attempt to improve on VTTS estimation. An Internet based survey for Katy Freeway travellers was used to collect data for this study. We used three different survey design strategies to produce surveys. We found that a random attribute level generation strategy, where the VTTS presented in the alternative was adjusted based on the answer to a previous SP question, performs better than other designs with respect to analysis of choice behaviour and estimation of VTTS. We analysed SP choices for travellers facing ordinary and six common urgent travel situations. We found that travellers value their travel time savings much more when facing most of the urgent situations. Due to this significant increase in the VTTS for travellers on urgent trips it is possible that the majority of ML travellers are on urgent trips. This includes travellers from all income levels, as even low income travellers on urgent trips value their time more than many high income travellers on regular trips. Therefore, using average VTTS will greatly underestimate the value of these MLs to travellers. This has significant policy implications since the benefits of MLs (and of most transportation investments) are primarily derived from travel time savings. Underestimating the value of ML travel time savings underestimates the benefits of MLs, reducing the likelihood of funding such facilities. Thus an important travel alternative would not be constructed. This study provides an important first step in proper estimation of these benefits using revised SP survey designs. (Author/publisher)
Abstract