This report represents an expert opinion provided to RACV by Professor Ezra Hauer, University of Toronto, Canada on two issues: The application of the case control methodology to research about the link between speed and crash risk and the validity of conclusions based on road research, and Whether there are alternative methodologies for assessing the link between speed and road safety. The report concludes that: Travel speed is thought to affect the chance of a crash to occur and the severity of the outcome of the crash once it has occurred. The latter is much easier to study, and is well supported from the findings of biomechanics of injury, The case control methodology is a valid approach to the estimation of relative risk in road safety. However, a weakness of the case control approach is the possibility of confounding, Estimates of crash risk based on two kinds of speed estimate can lead to bias in the relationship between estimated relative risk and speed, and A research program is outlined that is based on data obtainable from accident reconstructions and that can lead to a defensible lower bound estimate of the effect of change in the distribution of speeds on accident severity. (Author/publisher)
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