Abstract
Car emissions have significant detrimental environmental and health impacts, and many journeys could be undertaken using alternative transport. Effective transport policy necessitates identification of potentially modifiable determinants of driving. This thesis identified psychological underpinnings of decisions to drive. Study 1 used qualitative ‘grounded theory’ analysis to detail commuters’ reasons for driving, and highlighted misconceptions and biases underpinning these motives. In study 2, we developed quantitative measures of the concepts identified in study 1, and tested these as determinants of decisions to commute by public transport alongside variables from the Theory of Planned Behaviour (TPB; Ajzen, 1991). Results showed that the inductive concepts were best modelled as determinants of attitude and control perceptions, and demonstrated the superiority of established deductive concepts. A meta-analysis of the extant literature (study 3) showed a dearth of available evidence of correlates of driving. Strong associations with behaviour were found for intention and habit, and TPB cognitions relating to not driving showed stronger effects on intentions than did TPB variables relating to driving. There were also effects for descriptive and personal norms. Using an extended TPB model, study 4 demonstrated that the motivation to make local journeys by car was informed by cognitions relating to car and to non-car travel, and descriptive and personal norms. Environmental beliefs informed personal norms and attitudes to non-car travel. Studies 5-7 explored habit in commuting mode choice: study 5 developed a new self-report habit measure, which in studies 6 and 7 was used in comparison with existing habit indices to predict car and bicycle commuting among UK and Dutch samples respectively. Findings revealed the superiority of an existing habit measure, and pointed to the habitual nature of commuting mode choice. The seven studies highlighted motivational and volitional determinants of driving, and suggest various intervention strategies to reduce car use.