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

Introduction: Alternatives 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.
Methods: This 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.
Results: 99 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.
Conclusion: It 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.