Impacts of Red Light Photo Enforcement Cameras on Clearance Lost Time at Signalized Intersections

Red light running (RLR) is one of the most common violations drivers commit at signalized intersections. To avoid RLR violations, some drivers may decide to stop abruptly, even though they had the opportunity to cross the stop line before the onset of the red light. This action happens more frequently at the intersections with a red light camera (RLC). The consequence of this change in drivers’ stopping behavior is the potential reduction of the usable clearance interval and the slight decline in the intersection capacity. However, the Highway Capacity Manual (HCM) and the Alabama Department of Transportation (ALDOT) Traffic Signal Design Guide and Timing Manual take different approaches to estimate the clearance lost time (CLT) for capacity analysis of signalized intersections; there is not an adjustment factor for considering the impact of RLCs. In an attempt to quantify the effect of RLCs on the capacity of signalized intersections, field data were collected at eight intersections: four with RLCs and four without, in the cities of Opelika, and Auburn, Alabama. A total of 1,191 cycles and a total of 1,863 drivers’ responses to clearance intervals were used to estimate the CLT. It was found that the estimated CLT at the approach with a RLC is approximately 2.7 seconds longer than the default value presented by HCM and about 1.1 seconds longer than one estimated by ALDOT method. On average, the unused yellow time was a half second longer in RLC intersections than the intersections without RLCs.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Maps; References; Tables;
  • Pagination: 14p
  • Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

Filing Info

  • Accession Number: 01557805
  • Record Type: Publication
  • Report/Paper Numbers: 15-2245
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 30 2014 12:48PM