New Zealand’s rural intersection active warning system

This paper describes the development of NZ Transport Agency’s rural intersection active warning system (RIAWS) and summarises key outcomes from trials at six high risk intersections from around New Zealand. The RIAWS has the aim of reducing fatal and serious crashes at high risk intersections by reducing traffic speed when potential for a collision exists. Side road and right-turn vehicles at the intersection trigger a variable speed limit of 70 km/h on the through road, thus reducing both the likelihood and energy of crashes. At two intersections a ‘cross over’ study design was used to evaluate the relative effectiveness of electronic 70 km/h variable speed limit signs and “Slow down” warning signs. Motorist behaviour and perceptions since the RIAWS have been operational have been positive. Traffic speeds at the intersections when the 70 km/h speed limit sign is activated have reduced significantly although the “Slow down” sign was much less effective. Based on driver feedback from the initial pilot site, most drivers both support and understand the RIAWS. The findings suggest that while motorists do naturally moderate their speed slightly through rural intersections in the presence of potentially conflicting vehicles, the variable speed limit causes a more substantial speed reduction and is likely to significantly reduce casualties at high speed intersections.