Development of a Statewide Online System for Traffic Data Quality Control and Sharing

The Washington State Department of Transportation (WSDOT) operates thousands of Inductive Loop Detectors (ILDs) on the freeways and highways of Washington State. The collection and disbursement of this data is handled at the regional level, which has led to formatting differences and data fragmentation. The Datamart Project is intended to consolidate data from all regions and store it in one location easily searchable and accessible by all authorized users. Therefore a database and a web site have been created in a computer application called Datamart to accomplish these tasks and demonstrate the idea. Additionally, this research project has been also tasked with creating software applications for traffic sensor data acquisition and developing error detection and correction methodologies for data quality control. Error detection is accomplished in a three-step test proposed by this study to identify loop detectors suffering from severe errors. The default conditions used by this test approach are general enough to be applied in other states. Meanwhile, the approach also has its flexibility to use site specific parameters to optimize its performance at a specific location. These severe errors identifiable by this approach include wrong mode setting, cross chatting, extreme under sensitivity, and incorrect sensitivity level, among others. Loop detectors suffering from incorrect sensitivity levels may be adjusted by the proposed correction methodology. The correction methodology is designed to identify the true length of the loop detector’s detection zone. Properly calibrated ILDs are generally assumed to have detection zone sizes determined by the size of the loop coil buried in the roadway. The reality is that when ILD sensitivity levels drift from their correct settings, the detection zone size changes. By using the correct detection zone lengths, loop detector measurements can be corrected. This software-based approach is proven effective and can be retroactively applied to archived data as well. The loop error identification and correction algorithms have been implemented in the prototype Datamart system, which is an online database system backed up by Microsoft SQL Server 2008 and the Google Map technologies. It is highly scalable and has the potential to add new data sources from other transportation agencies and online analysis functions for regional transportation planning, traffic management, and analysis purposes.

  • Record URL:
  • Supplemental Notes:
    • This research was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    TransNow, Transportation Northwest

    University of Washington, Department of Civil Engineering
    129 More Hall, Box 352700
    Seattle, WA  United States  98195-2700

    Washington State Department of Transportation

    310 Maple Park Avenue, SE, P.O. Box 47300
    Olympia, WA  United States  98504

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    Office of the Secretary of Transportation

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
  • Publication Date: 2009-12


  • English

Media Info

  • Media Type: Web
  • Edition: Final Research Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 91p

Subject/Index Terms

Filing Info

  • Accession Number: 01152763
  • Record Type: Publication
  • Report/Paper Numbers: TNW2009-12
  • Contract Numbers: DTRT07-G-0010 (Grant)
  • Created Date: Mar 18 2010 2:02PM