Rural Intersection Active Warning System trialed in New Zealand demonstrates ability to slow down motorists, resulting in a 71 percent decrease in crashes.

A journal article reports the findings of a four year field operational test.

New Zealand

Summary Information

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.

The RIAWS consists of the following elements:
  • Side road high-definition radar sensors to detect approaching side road traffic approximately 150m from the intersection which then activate the main road electronic signs
  • Side road limit line sensors (cut loops) to detect waiting traffic and trigger the end of sign activation following a delay
  • Right turn bay sensors (where right turn bays exist) 50-66m from limit line, to activate signs, plus limit line sensors to detect queuing traffic and terminate sign activation following a delay
  • VSL signs, or 'Slow Down' signs placed in each direction on the main road approximately 150m from the intersection
  • A central control system to manage the RIAWS and accommodate data collection equipment
  • A Graphical User Interface (GUI) to remotely monitor the once-operational system in real-time.

    The RIAWS was trialed at 10 intersections categorized as "high-risk" around New Zealand where the effectiveness of the system on through-road vehicle speed was assessed and evaluated following a nearly four year activation period.

    Key Findings
    • The RIAWS was well received by the motoring public (as indicated by participants' survey responses)
    • The VSL sign was found to be more effective than an instructional sign alerting motorists to a potential hazard (i.e. 'Slow Down'). A key reason for this could be the credibility of the system, providing reasonable instructional information to support motorists’ existing perceptions of risk.
    • The crash rate and severity of injuries reduced significantly at the sites where RIAWS operated for up to four years. The overall crash rate reduced by 71 percent from 3.23 crashes per month to 0.92 crashes per month.
    Overall, the active nature of a Rural Intersection Active Warning System was found to increase driver state awareness, better prepare motorists for a possible event, and increase the gaps between potentially colliding vehicles.

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The signs they are a-changin': Development and evaluation of New Zealand's rural intersection active warning system

Author: Mackie, Hamish et al.

Published By: Journal of the Australian College of Road Safety

Source Date: 08/05/207

Other Reference Number: Volume 28, No. 3



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Benefit ID: 2018-01310