Performance of Modern Stop Bar Loop Count Detectors over Various Traffic Regimes

Accurate turning movement counts at signalized intersections are essential for retiming an intersection or corridor and also important for identifying trends in traffic data. In recent years, technology has emerged that can provide vehicle counts at the stop bar without sacrificing the performance of presence detection. The performance of these count detectors was investigated in two studies, which are reported in this paper. The studies involved the comparison of manual counts from recorded video with automated counts obtained from stop bar count detectors at a signalized intersection. These stop bar detectors are historically very difficult to obtain accurate count data from due to their long length (~50 ft) and tendency for multiple vehicles to concurrently occupy the detection zone. Recently, new detector amplifiers have been introduced that are designed to analyze the inductance profile to provide better stop bar counts. The first part of the study looked at count performance as a function of lane geometry and detector placement in the lane using data captured over a number of 24-hr periods. The placement of count detectors in relation to the lane lines was found to be a major factor in count accuracy leading to recommendations for sensor placement. The second portion of the study examined count detector performance under free-flowing and queued traffic regimes. A state of the art counting algorithm was observed to over count in the queued regime. Analysis of the relative change in inductance signature indicated a clearly defined signature was observable during free flow conditions, but the signature during saturated flow regime was quite complex an required more sophisticated analysis. It is expected that stop bar detection algorithms could be further enhanced if phase status information was provided to the count detector amplifier.

  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Smaglik, Edward James
    • Vanjari, Srinivas
    • Totten, Virgil
    • Rusli, Edhi
    • Ndoye, Mandoye
    • Jacobs, Allen
    • Bullock, Darcy M
    • Krogmeier, James V
  • Conference:
  • Date: 2007


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Photos; References; Tables;
  • Pagination: 20p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01049549
  • Record Type: Publication
  • Report/Paper Numbers: 07-1090
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 5:42PM