SP Surveys, Models and Results for the Values of Time and Reliability in Freight Transport in The Netherlands
G de Jong, M Kouwenhoven, Significance; P Koster, V van den Berg, Y-Y Tseng, E Verhoef, VU Amsterdam, NL; J Bates, John Bates Services, UK; L Tavasszy, TNO; P Warffemius, KiM Netherlands Institute for Transport Policy Analysis, NL
A new SP survey on the value of time and reliability was carried out among more than 800 shippers and carriers in The Netherlands. We present the survey design, the estimated choice models and the derived values
The freight values of time used in cost-benefit analyses of transport projects and policies in The Netherlands are based on stated preference (SP) research carried out in 2003/2004. For the value of travel time reliability, reliability ratios (expressing the value of reliability relative to the value of time) have been derived from the same survey, but this required many additional assumptions. This paper will describe the work carried out in a project for the Dutch Ministry of Infrastructure and the Environment to obtain up-to-date, evidence-based monetary values of time (VOTs) and values of reliability (VORs) in freight transport. The VOTs will be updates of existing values, the VORs will be the first of their kind for the Netherlands. This project also dealt with passenger transport, but this is treated in a separate paper.
The data collection for freight transport was carried out in 2010. Shippers and carriers were interviewed using computerised stated preference face-to-face interviews, resulting in a relatively large data base of more than 800 freight SP interviews. Specific target numbers of interviews were set for: transport mode used (road, inland waterways, sea, rail and air transport), containerised or not and shipper versus carrier. In considering the trade-off between time and money, carriers were steered to reflect on those time-varying items that are related to the provision of transport services (cost of staff and vehicles). Shippers that contract transport out were asked to consider the aspects of time related to the goods themselves (e.g. capital costs on inventory in transit). Finally, shippers with own account transport were requested to include all these time-related elements in their trade-offs.
The surveys include the following experiments:
- Within-mode experiment with six choice situations of two alternatives and two attributes: transport time and transport cost (following the set-up of the experiments on the national passenger VOT studies of 1988/1990 and 1997/1998);
- Within-mode experiment with two alternatives per choice situation, where each alternative is being described by four attributes: time, cost, reliability and arrival time (departure time is also presented, but is not independent of transport time and arrival time). In the first six choice situations, the expected arrival time is varied, in the following seven choice pairs, expected arrival time is kept constant.
For reliability, a non-graphical presentation through a series of five equi-probable transport times (and corresponding arrival times) for each alternative was used in the SP experiments.
For inland waterways and maritime transports we developed new SP experiments focusing on waiting time at a lock, bridge or terminal quay.
The first experiment can only give a VOT. The second experiment can give both VOT and VOR, also distinguishing between model specifications with and without explicit scheduling terms. The parameters needed for obtaining the VOR for cost-benefit analysis are estimated, using both the mean-standard deviation and the scheduling approach.
The interview data were used for the estimation of absolute and relative multinomial logit models on the SP data, with and without interaction variables and with and without variables to test elements of prospect theory (values for gains versus losses, non-linearities, inertia). The data did not support mixed logit (random coefficients) models. We accounted for repeated measurements among the same individuals by means of the Jackknife method.
The recommended VOTs and VORs will be derived on the basis of these estimation results and an expansion procedure. The project will be completed in June 2012.
The paper will present the design and results of the SP survey. It will contain statistics for the sample obtained, estimation results for the models mentioned above and the derived values of time and reliability. These values will be compared to those from previous surveys in The Netherlands and the international literature.
Association for European Transport