Reanalysis of travelling speed and the risk of crash involvement in Adelaide South Australia

Abstract

Modified logistic regression modelling was used to reanalyse free travelling speed case control data in an urban 60 km/h speed limit environment. An exponentiated second order polynomial function was used to model the relative risk of being involved in a casualty crash based on free travelling speed. The relative risk was found to approximately double for each 5 km/h increase in free travelling speed. This curve and the original data were then used to estimate the effects of various hypothetical speed reduction scenarios. Illegal speeding was found to be a major factor in casualty crashes and it was found that even very small reductions in the speeds of vehicles in general could be expected to result in a major reduction in the frequency of casualty crashes in an urban area.