Development and Field Assessment of Variable Advisory Speed Limit System

This paper presents the new Variable Advisory Speed Limit (VASL) system being operated in the Twin Cities, Minnesota, and its preliminary field assessment results. The new system has been designed to prevent the rapid propagation of the shock waves, emanated from fixed or moving bottlenecks, by gradually reducing the speed levels of the incoming flow. Using the traffic data collected from the loop detectors every 30 seconds, the system examines the deceleration patterns of the traffic flow in a given corridor and determines the locations and of the VASL control zones, whose lengths can vary depending on the current deceleration and speed levels at each zone. The VASL values of the available speed limit signs in each zone are calculated such a way that the effects of the speed control on travel times could be minimized. The preliminary analysis results with the before and after field data indicate that the average maximum deceleration in the VASL corridor during a peak period has been significantly decreased, while the increases in travel time have been moderate. Further, the peak-hour volume at a bottleneck in the VASL corridor has shown a slight, but significant increase compared to that of the before VASL period.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References;
  • Pagination: 9p
  • Monograph Title: 18th ITS World Congress, Orlando, 2011. Proceedings

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Filing Info

  • Accession Number: 01487173
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 18 2013 1:52PM