In this paper we report the results of a regional intervention study aimed at changing students' choice of the means of transportation by introducing a reduced fare semester ticket. First, we discuss and expand the concept of theory driven evaluation and relate it to the rational-actor theory used. The empirical results show that reduced cost produced by the intervention has a significant effect on behaviour but that this effect is mediated by attitudes toward the behaviour (preferences) and by perceived restrictions. Furthermore, the social process inherent in the intervention (polling of all students and mass media reports) also seemed to produce changes in the subjective norms. By using a structural equation model with latent means for two panel waves we have explicitly modelled the postulated set of propositions consisting of the substantive theory, the measurement model, and the action theory underlying the intervention. The results furnish complex insights on how the intervention was mediated by the constructs of a rational-actor theory - the theory of planned behaviour. Besides the significance of the variability of the price of public transportation for this population, the structural equation model yields information about the way attitudes, norms, subjectively perceived restrictions, intentions and behaviour itself are influenced. Furthermore, we can evaluate the stability of the constructs over time, allowing for both random and non-random measurement error. (A)
Samenvatting