Studies which systematically use well-established psychological theories for developing and evaluating interventions aiming at changing behaviour are rare. The present study uses Ajzen’s theory of planned behaviour (1991) as a theoretical framework for deriving hypotheses how an intervention (introduction of a collectively financed ”free”- ticket for public transport use by students) may influence the actual travel mode choice of students for university routes. Besides the evaluation of the overall effects of this intervention, the present study focuses on the detection of subgroups who are particularly responsive to the introduced intervention. For a more theory-driven conceptualisation of the subgroup-analysis we analysed individual differences in social value orientations (proself vs. prosocial orientation) which should be reflected in the importance given to outcomes prolifting personal vs. collective well-being. Because the intervention centres on changing the outcome ”price” which promotes personal well-being we expect that students with a proself value orientation should be more responsive to the introduced intervention. Data from a two-wave panel study were used to test these propositions. The intervention caused a drastic change in the actual travel mode choice of students: whereas the car-use decreased, the use of public transport increased considerably. The results of a structural equation model confirm the hypotheses derived from the theory of planned behaviour that the change in travel mode choice relies primarily on changes in behavioural and control beliefs caused by the intervention. The hypothesis that students with proself vs. prosocial value orientations react differently from the intervention was confirmed, too. The reaction of proself students was much stronger than that of prosocials. (Author/publisher)
Abstract