Safe speed for environment - Built environment indicator

Speeding is the biggest single behavioural factor involved in road deaths, contributing to around 40% of road fatalities each year in NSW. Speed limits are one of the simplest and most proven strategies for controlling and regulating driving speeds. Road user behaviour, including the perception of an appropriate speed of travel, can be influenced by the design and function of a road. Where possible, the speed limit of a road should be self-explaining. 

This indicator will support practitioners to understand whether the posted speed limit is safe and appropriate for the road and roadside environment, and whether the road should be nominated to TfNSW for a Speed Zone Review to be conducted (see notes). Based on the outcome of the assessment, practitioners can identify the safe and appropriate posted speed and compare it to the 85th percentile speed measurement, which will determine if additional supporting infrastructure and traffic calming measures are needed to achieve the desired travel speed outcome.

Practitioners can use the appropriate speed for the environment metric to determine whether a change in posted speed limit may need to be considered based on the surrounding context/activity.

Practitioners can use the 85th percentile speed metric to measure the speed at or below which 85% of vehicles are observed to travel under conditions past a nominated point at a certain time of day.