The signs they are a-changin’: Development and evaluation of New Zealand’s rural intersection active warning system
Submission Date: August 10, 2017 Journal
Suggested Citation: Mackie, H., Brodie, C., Scott, R., Hirsch, L., Tate, F., Russell, M., & Holst, K. (2017). The signs they are a-changin': Development and evaluation of New Zealand's rural intersection active warning system. Journal of the Australasian College of Road Safety, 28(3), 11-21.
In New Zealand, high-risk rural intersections are an important area of focus for reducing deaths and serious injuries. Accordingly, the Rural Intersection Active Warning System (RIAWS) was developed to reduce traffic speed on major road intersection approaches when the potential for a collision exists. Electronic variable speed limit (VSL) or ‘Slow Down’ signs on the intersection approaches are triggered by the presence of side-road and right-turning traffic, and when traffic clears the signs turn off. This paper reports on an evaluation of ten RIAWS sites, some of which have been active for four years. We found that the RIAWS was effective in reducing traffic speed when potentially colliding vehicles were present. However, the ‘Slow Down’ sign was significantly less effective than a 60 or 70 km/h VSL, and was subsequently discontinued. In the three-year period since implementation, fatal and serious crashes have almost been eliminated at the ten RIAWS intersection sites. The active nature of the system increases driver state awareness, better prepares motorists for a possible event, and increases the gaps between potentially colliding vehicles. Generally, it seems that RIAWS has lasting, rather than short-term speed reducing effects, and this may underpin the emerging safety benefits. Overall, RIAWS is feasible, operates well, tangibly reduces travel speed when a crash risk is present, is perceived positively by the motoring public, and has shown tangible safety benefits.