This paper reports the results of an econometric analysis of the influences on on-road behaviour of long distance truck drivers in Australia. The approach is couched in terms of a utility maximisation framework in which a driver trades-off economic reward with occupational risk. The physical risks to the driver due to driving while fatigued are proxied by the use of stimulants. Drawing on a 1990 survey of a sample of 402 truck drivers selected from owner drivers and employee drivers, we evaluate a number of alternative hypotheses on the relationship between drug taking, compliance with schedules and the propensity to speed. A system of structural equations is specified to test alternative hypotheses on causality between the endogenous variables and a set of exogenous effects. The models are estimated using distribution-free methods for mixed dichotomous and continuous variables. The main findings within the set of endogenous variables is that increasing speed is positively influenced by the propensity to take stay-awake pills which is itself positively influenced by the propensity to self-impose schedules. After controlling for a number of contextual influences on the endogenous variables, rates of financial reward have a significant impacts on all three endogenous variables. This study has highlighted the complex relationships which exist between speeding, social behaviour and economic reward
