An exploratory study on the safety effects of speed limit reduction policy in Brisbane and Melbourne CBDs

Transport authorities around the world have implemented a range of bicycle safety measures (minimum passing distance, helmet law, speed limit of motorized traffic, use of illumination equipment) to reduce the rate of crashes and thereby to enhance the level of cycling. However, a comparative assessment of the impacts of such interventions is rare because both the nature and time of interventions vary between jurisdictions. This paper presents an explorative study of the safety outcomes of a speed reduction policy in the Central Business Districts of two major cities in Australia (Brisbane and Melbourne). The paper used police reported historical bicycle crash data spanning over the period of 2006-2016 to evaluate the policy. Comparisons were made between before and after the implementation of the policy within a city, and between the cities using descriptive statistical analysis. Results show that the reduction of speed limits was associated with reduction in crash rates. However, the effect was more pronounced in Melbourne than in Brisbane. Challenges faced in evaluating the safety effects of the policies and the need for future research to robustly identify their impacts are discussed in this paper.