Effect of Daytime Running Lights on Left Turning Drivers’ Gap Acceptance

An observational field study was conducted by video recording traffic in clear weather during afternoon rush hours at two intersections. The purpose of the study was to determine whether drivers turning left from the main road onto the minor road across the path of approaching traffic were influenced in their gap acceptance decisions by daytime running lights (DRL) on approaching vehicles. Video recordings were analyzed to extract information about the size of 6711 temporal gaps available to turning drivers, whether the approaching vehicle had DRL or not, and several other factors. Clearance times between the turning vehicle exiting the intersection and the approaching vehicle entering the intersection were also determined from the video recordings. “Potential conflicts” between turning vehicles and approaching vehicles were defined based on short clearance times and decreases in the approaching vehicle’s speed. To determine the effect of DRL on gap acceptance at each site, the probability of gap acceptance was modeled (for 5125 available gaps less than seven seconds) with a logistic regression procedure that included effects of available gap size, DRL status of the approaching vehicle, approaching vehicle speed, approaching vehicle size, turning vehicle size, whether the available gap was the first gap encountered by the turning driver, and whether there were any vehicles queued behind the turning vehicle. Similar analyses were conducted for each site with available gaps less than four seconds. For all gaps taken, a separate model predicted potential conflicts based on effects of DRL, available gap size, and all other factors mentioned above. The results indicated that DRL on approaching vehicles did not significantly decrease the probability of gap acceptance suggesting that DRL may not encourage turning drivers to be more cautious. Despite the finding from one site that turning drivers were more likely to accept 3‐ to 4‐second gaps in front of approaching vehicles with DRL as compared to approaching vehicles without DRL, there was no evidence from this study to suggest that this effect would influence crash rates for left‐turn‐across‐path scenarios. DRL status of the approaching vehicle was not a reliable predictor of potential vehicle conflicts at either study site. Overall, the results do not provide evidence to support the use of daytime running lights as a countermeasure for fair weather daytime crashes involving right‐of‐way violations.

• Record URL:
  http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2011/811506.pdf
• 
• Corporate Authors:

  Westat

  1650 Research Boulevard
  Rockville, MD  United States  20850

  National Highway Traffic Safety Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Jenness, James W
  • Huey, Richard W
  • McCloskey, Shawn
  • Walrath, Jeremy
• Publication Date: 2011-10

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Figures; Maps; Photos; References; Tables;
• Pagination: 38p

Subject/Index Terms

• TRT Terms: Behavior; Daytime running lamps; Drivers; Field studies; Gap acceptance; Left turns; Operating speed; Right of way (Traffic); Traffic conflicts; Vehicle size
• Subject Areas: Highways; Safety and Human Factors; Vehicles and Equipment; I83: Accidents and the Human Factor; I91: Vehicle Design and Safety;

Filing Info

• Accession Number: 01367864
• Record Type: Publication
• Report/Paper Numbers: HS-811 506
• Contract Numbers: DTNH22‐05‐D‐01002
• Files: HSL, TRIS, USDOT
• Created Date: Apr 13 2012 3:54PM