Feasibility of a randomised controlled trial of financial incentives to promote alternative travel modes to the car

Abstract

IntroductionAlternatives to the car, such as walking, cycling and public transport can integrate physical activity into everyday life. Interventions promoting alternatives to the car targeting individual behaviour have shown modest effects, and supportive environments appear important. MethodsThis mixed-method study assesses the scientific and operational feasibility of conducting a randomised controlled trial (RCT) of individual financial incentives within a supportive physical environment. We invited residents of Northstowe, Cambridgeshire, UK who had not previously claimed financial incentives to complete a baseline questionnaire assessing socio-demographic characteristics and travel behaviour. On completion, households were randomly assigned to (1) control – claimed incentives online; (2) intervention - received incentives via email; and (3) intervention plus - received greater value incentives via email. We assessed incentive use via questionnaires at three and six months. Longitudinal qualitative interviews at baseline, three months and six months elicited views of incentives and factors influencing use. Results99 residents from 88 households (household response rate: 88/475 (19%)) completed the baseline questionnaire and were randomised at household level. The local authority delivered all incentives. Compared to the control group, incentive use was higher in the intervention and intervention plus groups at six months, but there was little difference between intervention and intervention plus group. Qualitative data suggests that incentives worked by prompting existing intentions, raising awareness of alternative travel modes and to a lesser degree by reducing travel cost. This resulted in some new leisure travel behaviour, but most often to subsidise existing travel. Qualitative data suggests that existing travel preferences and environmental conditions influenced incentive use. ConclusionIt is feasible to deliver an RCT in collaboration with a local authority and future trials should account for recruitment challenges. Reducing the effort required to obtain incentives increased their use, but future research should investigate the surrounding enabling environmental contexts.