Testing the capacity within an extended theory of planned behaviour to reduce the commission of driving violations

Abstract

The capacity within an extended theory of planned behaviour (TPB) to change young drivers’ intentions and reduce their commission of driving violations was tested using regression-based statistical simulations. Participants (N = 198) completed questionnaire measures of TPB variables, plus moral norm and anticipated regret, each with respect to 11 different driving violations. One month later, subsequent behavioural performance was measured, again using self-completion questionnaires. Statistical simulations indicated substantial capacity within the extended TPB to reduce driving violations, with maximum changes to all of the cognitive predictors generating large degrees of intention and behaviour change (i.e. d > 0.80). However, the degree of intention change that was generated was greater than the degree of behaviour change, and sensitivity analyses demonstrated that behavioural interventions need to successfully change multiple cognitive variables in order to achieve meaningful reductions in driving violations. Implications of the findings for developing behaviour change interventions are discussed.

Keywords:

• extended theory of planned behaviour
• cognition and behaviour change
• statistical simulations
• driving violations
• young rivers

Notes

Notes

1. Note that the relationships between antecedent cognitions and intention, as proposed by the model specified in Figure 1, is expressed as: INT =  _{w 1} ATT +  _{w 2} SN +  _{w 3} PC +  _{w 4} MN +  _{w 5} AR (where INT is intention, ATT is attitude, SN is subjective norm, PC is perceived control, MN is moral norm, AR is anticipated regret and w1, w2, w3, w4 and w5 the parameters indicating the relative importance of attitude, subjective norm, perceived control, moral norm and anticipated regret, respectively). Given that the extended TPB proposes the same predictors of behaviour as does the originally formulated TPB, the formula for the relationships between extended TPB constructs and behaviour is the same as specified in Section 1.1 (i.e. BEH = _w1 INT +  _{w 2} PC).

2. For brevity, the full range of scenarios is not presented in this article but it is available from the author on request.

3. Note that principle components analyses (varimax rotation) did not provide evidence for the separation of instrumental versus affective attitude, injunctive versus descriptive norm or self-efficacy versus perceived controllability (e.g. with few exceptions, the items measuring instrumental and affective attitudes loaded onto the same factor). Therefore, the measure of attitude was computed by taking the mean of the instrumental and affective attitude items, aggregated across the 11 driving violations. Similarly, the measure of subjective norm was computed by taking the mean of all the injunctive and descriptive norm items across the 11 driving behaviours, and the measure of perceived control was computed by taking the mean of all the self-efficacy and perceived controllability items. It should also be noted that principal components analyses showed that the intention items loaded almost exclusively onto a single underlying dimension, as did the behaviour items (reported commission of the 11 driving violations), which is consistent with previous research examining convergence among driving violations (e.g. Reason et al. 1990). Furthermore, when the analyses presented in this article were re-run for each driving violation separately, a largely consistent pattern of results emerged for each one. Thus, overall, there was strong evidence for convergence among the driving violations examined in this study, supporting the decision to aggregate across driving behaviours.

4. In order to avoid over-estimating the effects on intention, participants’ scores on the cognitive predictors were not permitted to exceed the scale end points in these sensitivity analyses. For instance, if a large (0.8 SD) change in a participant's attitude score resulted in a value lower than −4, that participant's attitude score was set to −4 (i.e. the most negative attitude possible towards committing driving violations).

5. Note that a separate analysis was performed in which behaviour was regressed on all of the cognitive predictors in the extended TPB. Consistent with theory, only intention and perceived control had direct independent effects on behaviour.