The valuations of prices and costs of travel times appear to be key parameters in the calibration of any demand traffic simulation systems. However, it seems that practical requirements are fogging the real nature of these concepts, which should be strictly related to the individual preferences and behaviours, but are also depending on the travel alternatives and their corresponding effective levels of supplied attributes. Thus individual specific values of travel times should change with the attributes levels and with transportation mode specific tastes and behavioural considerations. First, theoretical approaches on the topic have considered the time component as a scarce resource. However since the consumer is not always the producer of his/her activities, particularly in travel activity, the user is a time-taker and rationally knows that he/she has to account for a minimal amount to be spent. Then, time resources are different from travel time, and the travel time can be split into different components: access/egress times, waiting times, commuting times and riding/on-board times and have found significant values of travel time savings. Another general important standpoint is to differentiate the several reasons why the travel time has to be allocated. The basic idea is that the activity to be realised at destination does not improve the same way the well-being of the individual. Thus, the corresponding needed travel time to access it does not take the same importance in the mind of the individual. This implies different preferences for different situations, and has led to activity-based travel demand systems. In this paper on the regular journey-to-work (JTW) is considered. It is observed that most of the empirical applications have used functional forms with pre-specified properties for the implicit valuations of travel portfolios attributes, such as income effects. It has also highlighted that the travel time may be unreasoningly quantified. It is possible to account for these effects using simple transformations of the corresponding variables, but it is argued that this is a misleading approach, since it is based on a priori behavioural considerations that are simply leading to pre-specified results. A regular journey-to-work transportation mode choice model was developed, within which the traveller is faced with mutually exclusive alternatives, each supplying distinct travel portfolios. The decision process of a rational traveller is described. Definitions are derived for the concepts of prices and values of travel times. It is shown that there are different situations emerging according to the capacity of endogenising leisure patterns during the OD trip, defining behavioural profiles for the traveller, so that the effective travel time may be twisted by the individual who may not strictly quantify it. An income effect is also included, entering the willingness to pay for the time-saving attributes. The cost of time is specific to the individual and to the alternative. A binomial Box-Cox Logit model, particularly adapted for joint estimation of tastes and behaviour parameters, was developed. Some estimates of the parameters of the theoretical value of time functions in French Parisian region were developed using an updated 1998 sub-sample of the large regional travel survey. For the covering abstract see ITRD E124693.
Abstract