Safety Performance Functions for Bicycle Crashes in New Zealand and Australia

After decades of decline, recreational and commuter cycling are becoming more popular in many Australasian cities. This renewed popularity is encouraging from the perspectives of sustainable transport and public health. A major concern to governments at all levels, however, is the higher crash risk that cyclists face, compared with drivers or passengers in motor vehicles, particularly when cyclists ride on roads. Transportation professionals should understand the level of risk that cyclists face within various parts of the road network and the measures that can be employed to mitigate that risk. This paper presents research findings from three main safety studies undertaken in New Zealand with the use of data from cities in New Zealand and in Adelaide, Australia. The research involved both generalized linear modeling and before–after, control–impact methods. Across the various studies, crash, traffic, and cycle volumes and layout data were collected for urban road links, traffic signals, and roundabouts. Flow-only models demonstrated a safety-in-numbers effect: crash risk per cyclist was shown to be lower as cycle volumes increased. When other variables were added to the models, it was possible to understand the impact on various crash types of factors such as road section length, motor vehicle speed, visibility, presence and type of cycle facilities, and lane and road width. Before-and-after analysis was employed to help identify the presence of any bias in the sites that had received cycle facilities. Research findings were mixed on the capacity of cycle facilities to improve safety. Well-designed facilities of adequate width and painted with color appeared to perform best.