Flagger Effects in Reducing Likelihood of Rear-End Collisions in Work Zones

Rear-end collisions are among the most dominant crash types in work zones. This study explores the effectiveness of flaggers in reducing the frequency of very short headways and the likelihood of rear-end collisions in work zones. To assess the effectiveness of flaggers, eleven data sets were collected from five single-lane work zones with no lane change opportunity. Time gap and speed data of more than 6,250 vehicles were used. Statistical analyses were made based on the frequency of three risky driving behaviors that may lead to rear-end collisions: I) Maintaining “short” time gaps (i.e. following “too closely”), II) Speeding by at least 5 mph at “short” time gaps, III) Faster-trailing by at least 5 mph at “short” time gaps. Based on the distribution of driver reaction times, three different upper thresholds were used to define “short” time gaps: 0.70 s, 0.85 s, and 1.00 s. The results indicate that flagger presence significantly reduced the probability of a vehicle’s following “too closely” by around 60% to 69%. Likewise, it led to an 85%-to-95%- reduction in the probability of a vehicle’s speeding by at least 5 mph at “short” time gaps. Notwithstanding these, the frequency of faster-trailing by at least 5 mph at “short” time gaps was found to be trivial whether there was flagger or not. Yet the flagger presence was a key factor that significantly reduced the likelihood of rear-end collisions at the study sites.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee AHB55 Work Zone Traffic Control
  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Avrenli, K A
    • Benekohal, R
    • Ramezani, H
  • Conference:
  • Date: 2012


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 15p
  • Monograph Title: TRB 91st Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01374320
  • Record Type: Publication
  • Report/Paper Numbers: 12-1878
  • Files: TRIS, TRB
  • Created Date: Jun 28 2012 8:52AM