Evidence that implementation intentions reduce single-occupancy car use in a rural population: moderating effects of compliance with instructions

Implementation intentions have successfully changed a range of behaviours, but remain relatively untested in populations that might be less compliant with instructions than students. Four hundred and fifteen rural dwellers were randomly allocated to receive questionnaires only or a questionnaire furnished with an implementation intention instruction. Three hundred and fifty-two were successfully contacted again and provided follow-up data. The main outcome measure was single-occupancy car use; theory of planned behaviour variables were used as secondary outcome measures. Findings revealed that, across the full sample, implementation intentions successfully arrested an increase in single-occupancy car use, F(1, 365) = 4.62, p < 0.05, eta(2)(p) = 0.01. Compliance with the instructions was low (25%) and significantly affected the findings: Whereas the single-occupancy car use of compliers significantly decreased, F(1, 51) = 7.39, p < 0.01, eta(2)(p) = 0.13, the single-occupancy car use of non-compliers significantly increased, F(1, 155) = 12.14, p < 0.01, eta(2)(p) = 0.07. Non-compliers were significantly less motivated to change their behaviour at baseline, F(5, 179) = 6.11, p < 0.01, eta(2)(p) = 0.15. The findings provide support for the use of implementation intentions to promote pro-environmental behaviour in a rural population, but further research into the causes and consequences of non-compliance is required.