Modelling the impact of lower speed limits on residential streets for cyclist level of traffic stress and car travel time in Greater Melbourne

Abstract

Reducing speed limits to create safer, lower-stress environments for cyclists is a widely proposed policy but often faces resistance due to concerns about increased travel times. This study evaluates these concerns by assessing Level of Traffic Stress (LTS) under existing speed limits (base scenario) and the effects of reducing residential street speed limits to 40 km/h and 30 km/h (alternative scenarios) on cycling LTS and car travel time.

LTS is a widely used measure of cycling stress, categorising road segments from LTS-1 (least stressful) to LTS-4 (most stressful). We assigned LTS values to all road segments in Greater Melbourne based on cycling infrastructure, road hierarchy, traffic volume, and speed limits from OpenStreetMap. Trips from a government travel survey were then routed through the network to estimate exposure to different LTS levels under base and alternative scenarios. Additionally, a mode choice model was developed to examine the impact of LTS exposure on cycling likelihood. Finally, an agent-based transport model was used to evaluate the impact of this intervention on car travel time.

Results showed significant reductions in high-LTS exposure with lower speed limits. Under the base case, 27.9% of routes were on LTS-1 roads, and at 30 km/h this increased to 63.3%. Mode choice model results confirmed a strong negative correlation between cycling likelihood and high-LTS exposure. Car travel time impacts were minimal, even for trips largely on residential streets the average was only one minute.