The Challenge

Auckland Transport wanted to develop a new prioritisation strategy for investigating road safety countermeasures in the Auckland Region.  Auckland has many intersections with a Collective Risk rating (total crashes) and/or Personal Risk rating (crashes per vehicle) of medium-high or high. In many instances the remedial costs can be high.  There is a need for a means of identifying those intersections where minor safety (low cost) interventions can generate road safety benefits.

The Solution

Develop and apply a methodology which incorporates Level of Safety Service (LoSS) in addition to Collective and Personal Risk .  The LoSS for an intersection is determined from the annual traffic flows on each leg (AADT) and the number of crashes in a 5-year period.  The very worst intersections generally have both a high Collective and Personal Risk. The LoSS indicator identifies intersections that have high Collective Risk or high Personal Risk and perform poorly compared to similar intersections.  These often have inherent flaws that make them more dangerous, but can be readily mitigated.

The Outcome

The process is being used to produce a prioritised list of 50 intersections which are recommended for further investigation for safety improvements.