ITS data quality : assessment procedure for freeway point detectors.

54101003Final contract report;July 2002Dec 2003.PDFTech ReportFHWA/VTRC 04-CR10VirginiaVirginia Transportation Research CouncilSmith, Brian L.,Venkatanarayana, RamkumarSmith, Clinton DMcGhee, Catherine CPerfater, Michael AVirginia Transportation Research CouncilVirginia. Dept. of TransportationUnited States. Federal Highway AdministrationUS Transportation CollectionThe Virginia Department of Transportation (VDOT) has made significant investments in the traffic-monitoring infrastructure that supports intelligent transportation systems (ITS). The purpose of this infrastructure is to provide accurate, real-time information on the status of the transportation system; thus it is critical that the monitoring infrastructure provide accurate data. Although detectors are usually tested immediately after installation, it is well known that they operate in a very harsh environment and thus are susceptible to degradation in accuracy and/or complete failure. Consequently, a long-term commitment to data quality assurance is required through maintenance, data quality assessment testing, and repair/replacement. The quality of data from ITS applications is becoming increasingly important as the data are more widely used. Not only is the data used in real-time operations, but also in myriad other, often more traditional, transportation applications. The purpose of this research project was to develop a procedure that VDOT could use to assess its ITS data quality. The report includes a data quality assessment procedure that is based on theory, practice, and empirical investigation. The procedure has the following key features: benchmark data collection using temporary installation of non-intrusive detectors; data quality assessed at the lane level to pinpoint problem detectors; data quality assessed at the 1-minute interval (or minimum practical measurement interval) level to provide sufficient quantities of data in reasonable periods of time; analysis techniques including both measures and plots, which provide quantitative and visual indications of data quality. The authors recommend that VDOT begin to use the procedure on both an ad-hoc basis and in a statewide program as a means of protecting its significant investment in ITS data collection