Want to comply with speed limits? Can comply with speed limits: Effectiveness of behavioural planning for increasing drivers' compliance with speed limits

Research on general population car drivers shows that, in general, drivers are strongly motivated to comply with speed limits (e.g. they have positive attitudes and intentions from a road safety perspective; Elliott, Armitage & Baughan, 2003). However, about a quarter of drivers do not often comply with the speed limit despite being motivated to do so (Elliott, Armitage & Baughan, 2007). The present study therefore tested the effects of a behavioural planning intervention designed to increase compliance with speed limits for this group of drivers. More specifically, the study tested whether specifying an implementation intention (Gollwitzer, 1993) increased drivers' compliance with the speed limit. Participants (N=300) were randomly assigned to either: (a) a control condition or (b) an experimental condition, in which they specified an implementation intention (identified situations where they find it difficult to comply with the speed limit and self-generated strategies for coping with these situations). Motivation to comply with speed limits (variables from the theory of planned behaviour; Ajzen, 1985) and self-reported behaviour were measured at both baseline and, one month later, at follow-up. Results showed that compliance with speed limits significantly increased in the experimental group but not in the control group. Consistent with previous research on implementation intentions in other domains, this effect could not be accounted for by an increase in motivation (e.g. a change in attitudes or intentions to speed). The results also showed that implementation intentions weakened the relationship between past and future speeding behaviour and strengthened the relationship between intention and future speeding behaviour, implying that they 'worked' by breaking the effects of habit and by helping drivers to realise their intentions to comply with speed limits. From an applied perspective, the results demonstrate the usefulness incorporating behavioural planning strategies into road safety interventions.