Assessing the Impact of Speed-Limit Reduction near Signalized High-Speed Intersections Equipped with Advance-Warning Flashers

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Assessing the Impact of Speed-Limit Reduction near Signalized High-Speed Intersections Equipped with Advance-Warning Flashers

Sharma, Anuj

AbstractAn advance-warning flasher alerts drivers of the imminent onset of a yellow light at a signalized intersection, and it is widely used to reduce crash frequency and severity. Recently, a more-aggressive countermeasure, a speed-limit reduction, is being used at high-speed signalized intersections in addition to advance-warning flashers. In this paper, six high-speed intersection approaches in Nebraska were evaluated to assess the operational effects of no speed-limit reduction, an 8.0 km/h (5 mi/h) speed-limit reduction, and a 16.1 km/h (10 mi/h) speed-limit reduction in the vicinity of high-speed signalized intersections equipped with advance-warning flashers. The placement of speed-limit-reduction signs resulted in significant reductions in observed speeds only when upstream drivers were traveling at speeds higher than a comfortable range—1.8 to 4.0 km/h (1.1 to 2.5 mi/h) higher than the regulatory speed limit. The likelihood of this condition being satisfied was higher in case of 16.1 km/h (10 mi/h) drop; however, it was not found to be true when the speed limit was dropped by 8.0 km/h (5 mi/h). Also, the compliance rates to the regulatory speed limit varied from 15 to 85%, highlighting the fact that ambient conditions have a much greater influence on drivers’ speed choices as compared to the regulatory speed limit. This research provides further evidence that speed-limit reductions, in conjunction with advance-warning flashers, appears to be an effective safety countermeasure; however, their effects will be dependent on the amount of speed-limit reduction and observed speeds.