Effects of Te Ara Mua – Future Streets Suburban Street Retrofit on Traffic Speed and Volume: Controlled Before-After Study

Abstract

Traffic speed and volume are important determinants of road traffic injury rates for all travel modes, and high traffic speed and volume can deter walking and cycling. Te Ara Mua – Future Streets is a project in Māngere, Aotearoa New Zealand, that aims to make it safer and easier for people to get around their local neighbourhood, especially by walking and cycling. Key components include implementation of a street hierarchy and street design changes to reduce speeds on local streets, as well as other components including improved active transport infrastructure. We used tube counters to measure motor vehicle speed and volume before and after the intervention, at different levels of the street hierarchy: arterial, collector and local streets. A difference-in-differences approach was used to assess changes in the intervention area compared with a matched control area. We found post-intervention mean speed reductions of 8 km/h on local streets, and 5-6 km/h on collector streets, relative to the control area. Mean traffic volumes reduced by 17-24% on local streets, with no change on collectors or arterials. Both post-intervention time points showed similar results, indicating a sustained effect. Overall, this intervention successfully reinforced a street hierarchy, creating local residential streets that are more conducive to road safety and active travel. Implementation of similar interventions in disadvantaged neighbourhoods could help reduce road traffic injury inequities. Our future research will evaluate broader impacts of this intervention on travel mode shift, injury rates and other health and social outcomes.

Keywords: Road traffic injuries, speed, traffic volume, intervention, street hierarchy, human factors