Promoting compliance with speed limits: Testing a theory driven intervention based on the theory of planned behaviour

Elliott, M.A. and Armitage, C.J. (2008) Promoting compliance with speed limits: Testing a theory driven intervention based on the theory of planned behaviour. In: 4th International Conference on Traffic and Transport Psychology, 2008-08-31 - 2008-09-04. (Unpublished)

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Abstract

The theory of planned behaviour (TPB; Ajzen, 1985) has received unprecedented research attention. However, in the context of drivers' speeding behaviour, just one published study (Parker et al., 1996) has used the model to both develop and experimentally test an intervention, although several studies have used the TPB's framework to evaluate interventions. Furthermore, TPB-intervention studies on general social behaviour have a number of limitations. Few studies employ randomised controlled designs, intention-to-treat analysis and standardised, reliable measures of TPB constructs (Hardeman et al., 2002). Also, few studies examine whether intervention effects on intentions and behaviour are mediated by the model's components. However, mediation analyses can help establish how an intervention works and provide evidence on the causal relationships posited by the TPB. Overall, there is limited empirical evidence for the TPB as a basis for behaviour change interventions. The present study therefore aimed to develop and test an intervention based on the TPB. It was hypothesised that the intervention would promote drivers' compliance with speed limits via changes in the model's psychosocial components. Participants (N = 300) were randomly assigned to an experimental condition, in which they received persuasive messages designed to change beliefs as specified in the TPB, or a control condition. Postal questionnaires were used to collect both baseline and follow-up (one month post-baseline) measures of TPB variables and behaviour. Results showed that the intervention had a significant effect on one control belief, perceived behavioural control and behaviour (all effects in the expected direction). The effect of the intervention on perceived behavioural control was mediated by the control belief and the effect on behaviour was, in turn, mediated by perceived behavioural control. Theoretical and applied implications of the findings will be discussed in relation to promoting road safety.