Application of infrastructure risk rating (IRR) to support speed limit reduction in Western Australia

The Infrastructure Risk Rating (IRR) methodology developed in New Zealand assesses road safety risk based on infrastructure, roadside hazards and land use elements. The methodology was applied to 110km/h posted speed limit state roads in Western Australia (WA) to support speed limit review. After identifying medium to high-risk road sections based on IRR scores, stakeholders reviewed the results, considering route hierarchy, surrounding network and implementation issues. As a result, a number of road sections were identified as priority sections that warrant speed limit reduction.