The Effects of Gift Vouchers and Environmental Certificates on the Demand for a Collective DRT System

This paper analyzes in a large-scale field experiment (N = 1,425) whether gift vouchers stimulate the demand for DRT. This scenario is compared to a situation where customers receive environmental certificates, which report the saved carbon dioxide as a consequence of the bus ride. In our two treatments, the gift vouchers and the environmental certificates could be gained by reaching to a certain threshold of rides with the DRT service (EcoBus). The data show that gift vouchers excellently work to increase the demand for DRT. EcoBus rides increased by 83\% in the intervention phase. Interestingly, the certificates also have a positive effect and lead to an increase of 65\%. However, gift vouchers outperform them, as the increase in rides is attenuated in the end of the certificate-treatment phase.