Carpooling stated preference (SP)

Abstract

A recent study aimed to estimate the potential of carpooling in Switzerland. Part of this study was a survey in which the attitude of the public towards this transport option was investigated using both multi-response questions and stated preference (SP) experiments. In order to gain an insight on how innovative modes are perceived in general, the SP part was composed of two different experiments, one of them including carsharing as alternative. In the first experiment respondents were choosing among car, public transport, carpooling as driver and carpooling as passenger. In the second experiment respondents were choosing among car, public transport and carsharing. This paper reports on the multinomial logit choice models, which were estimated based on participants’ responses. Both SP experiments were based on a trip reported by participants during a phone interview. For each experiment two specifications, a linear and a nonlinear one were estimated. The nonlinear specification allows investigating the impact of selected socio-demographic variables, in this case income and travel time, on the parameters of the models and on willingness to pay indicators. Such indicators permit to complement the qualitative discussion of the results with quantitative analyses and provide a useful background for policy evaluation and planning. Experiment 1: Carpooling In the first SP experiment four alternatives were considered: car, public transport, carpooling as driver and carpooling as passenger. Each respondent received eight situations and was invited to choose the preferred alternative. The respondent’s burden of having to choose among four alternatives in each situation was a concern. For this reason respondents were randomly assigned to one of three groups, each of them corresponding to a combination of three of the four modes listed above. By limiting the burden on the respondents, this strategy keeps the response rate high. The large sample was supposed to guarantee the statistical significance of the results despite each alternative mode being evaluated in a smaller number of cases. The three combinations proposed were: - Car – Public Transport – Carpooling as driver - Car – Public Transport – Carpooling as passenger - Car – Carpooling as driver – Carpooling as passenger For carpooling it was assumed that gasoline cost would be simply split between driver and passenger (50% each). Travel distance was considered the same as for the mode car (and consequently the cost for gasoline) while travel time was increased by five minutes to take into account waiting times at the meeting point. Parking for the driver was as for the mode car. It was also considered that a few times per year driver and passenger would miss each other and thus need to reorganize the trip. The ranges of attributes for this experiment are shown in Table 1. Those ranges were chosen with the aim to be large enough in order to induce change in the behavior of respondents but still be realistic. No particular assumptions on future developments of prices or travel times were made.