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Deployment of a Virtual Sensor System Based on Probes, in an Operational Traffic Management System


The Washington State Department of Transportation (WSDOT) operates a central traffic management system (TMS) for both day-to-day surveillance and traveler information. Past efforts developed the ability to create real-time traffic speed information by using virtual sensors that are based on transit vehicle tracking data.

This project developed a way to provide real-time congestion information from Seattle area arterials and freeways to the WSDOT TMS by using the Intelligent Transportation System Backbone. This system harvests existing automatic vehicle location (AVL) data from within King County Metro Transit and transports the raw data to the UW, where a series of operations converts the data into roadway speed information. This roadway speed information is color coded on the basis of specific, localized conditions for the arterials and freeways to reflect traffic congestion. The resulting traffic data product is then provided to WSDOT as a virtual sensor data source for roadways where presently there are no inductance loops. The project also created several user interfaces for traveler information, including a Java application that displays the spatial and temporal average speeds of transit vehicles on a map of the major arterials and freeways and a type of traveler information map.

This report also includes a quantitative evaluation of transit vehicles as traffic probes. A comparison of statistics between virtual sensors based on transit vehicles as probes and those from speed traps presently used by WSDOT suggested this virtual sensor technology can be used to identify both recurring and non-recurring congestion with the accuracy associated with speed traps. This means that additional roadways that do not presently have speed traps can be instrumented without installing equipment in the roadway.

  • Date Published: November, 2006
  • Publication Number: WA-RD 660.1
  • Last Modified: March 27, 2007
  • Authors: Daniel J. Dailey, Frederick W. Cathey.
  • Originator: Washington State Transportation Center (TRAC)
  • # of Pages: 38 p., 1,422 KB (PDF)
  • Subject: Probe vehicles, Vehicle sensors, Public transit, Bus transit, Loop detectors, Traffic speed, Arterial highways, Traffic congestion, Intelligent transportation systems
  • Keywords: Probe vehicles, virtual sensors, transit buses, loop detectors, quantitative analysis, congestion map, arterial highways.
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This abstract was last modified January 26, 2009