Sequential Dynamic Curve Warning System reduces the number of vehicles exceeding the speed limit by 10 mph or more by 27.8 percent

Field tests in 5 U.S states attempt to reduce crashes on horizontal curves on rural roadways.

January, 2014

Summary Information

As part of a national evaluation, Traffic and Parking Control Co. (TAPCO) installed and tested the Sequential Dynamic Curve Warning System (SDCWS) in 5 U.S states. The SDCWS works to guide drivers through upcoming horizontal curves and warn speeding drivers to slow down. This study evaluated the effectiveness of the system in reducing vehicle speeds as well as the frequency and severity of speed-related crashes.

  • 12 treatment sites and 24 control sites in Iowa, Missouri, Texas, Washington, and Wisconsin were studied. The system was installed at each site during the summer of 2012.
  • The installed system consisted of a series of LED-enhanced solar powered chevron signs and wireless controllers along with ultra-low power radar. The signs and radar operational settings were calibrated specifically for each location, with the quantity of signs and speed of the curve determining the speed of the sequence and flash duration.
  • Data was collected before and immediately after the installation as well as at 12 months, 18 months and 24 months post-installation. Speed data was collected from pneumatic road tubes.

  • After one year, vehicles exceeding the speed limit by 10 mph or more decreased by 27.8 percent.
  • Sites reported crash reductions ranging from 45-100 percent.

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Evaluation of the TAPCO Sequential Dynamic Curve Warning System

Author: Omar Smadi, Neal Hawkins, Shauna Hallmark, Skylar Knickerbocker

Published By: Federal Highway Administration 1200 New Jersey Avenue, SE Washington, DC 20590

Source Date: January, 2014



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Benefit ID: 2015-01022