Long term safety benefits of highway safety reviews: case control comparisons with unreviewed highways
Across Australia rural high speed roads have markedly poorer safety records than urban roads. Highway safety reviews are a unique methodology involving multidisciplinary safety focussed physical inspections of highways and fatal crash locations, along with detailed crash analysis. Reviews are based on safe system principles rather than an audit of conformity with guidelines. A program of works is developed based on the review. We have previously reported clear road safety gains based on shorter post-review data. However, these gains occurred during broader reductions in the NSW road toll, raising the possibility that the highway review gains were simply part of a bigger improvement. Alternatively these gains could have been due to regression to the mean. The current paper presents a comprehensive rigorous evaluation, with the following improvements of methodology: a two by two design of pre versus post data by reviewed highways versus unreviewed control highways treated with conventional blackspot programs; based on the extended post works casualty data (four years); analysis of both fatalities and injuries. These analyses allow resolution of regression to the mean account, and direct comparison of the highway review versus the usual blackspot approach. Results reveal large safety benefits of the highway reviews exceeding those of conventional blackspot treatments, not explicable in terms of regression to the mean or broader gains in NSW. Results are discussed in terms of strategic and procedural differences between the review and blackspot approaches. Recommendations are made for a refined approach to engineering works to improve safety outcomes.