Two-Lane to Three-Lane Roadway Conversions: Active Transportation Safety Implications

Land development patterns often shift two-lane collector roadways from serving primarily through traffic to accommodate a greater mix of through and local access traffic. In other cases, local destinations remain while downstream development increases through-traffic demand. In both scenarios, turning movements and through traffic increasingly conflict with each other. Where no alternative corridor options exist, through traffic remains on the road along with increased traffic volumes generated by new land uses. Prior to development, these roads may have included paved shoulders occasionally used by pedestrians, though active transportation activity was generally limited because fewer nearby destinations existed. As development intensifies, pedestrian activity increases alongside turning conflicts, creating pressure on agencies to widen the roadway cross-section by adding center turn lanes or sidewalks. The objective of this research is to evaluate and compare the safety performance of two-lane roadway cross-sections without dedicated turn lanes and three-lane cross-sections with center two-way left-turn lanes along corridors that include treatments or countermeasures to protect vulnerable road users. The research will identify the traffic, land use, and operational conditions under which each cross-section is more effective at improving safety for motorists and vulnerable road users while balancing multimodal operational performance. A secondary objective is to develop a guide with evidence-based recommendations, design considerations, and implementation strategies for improving multimodal safety along suburban and urbanizing corridors with current or projected high through-motorist travel and left-turn motorist demand.

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=6058
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Status: Proposed
• Funding: $600,000.00
• Contract Numbers:

  Project 17-153

• Sponsor Organizations:

  State Departments of Transportation (participating member states of American Association of State Highway Transportation Officials (AASHTO))

  American Association of State Highway Transportation Officials (AASHTO)
  444 North Capitol Street, NW
  Washington, DC  United States  20001

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Managing Organizations:

  National Cooperative Highway Research Program (NCHRP)

  Transportation Research Board
  500 Fifth Street, NW
  Washington, DC  United States  20001
• Project Managers:

  Deng, Zuxuan

• Start Date: 20261001
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Bicycle lanes; Bicycle safety; Development; Highway design; Land use; Pedestrian safety; Sidewalks; Traffic safety; Traffic volume; Turning lanes
• Subject Areas: Design; Highways; Operations and Traffic Management; Pedestrians and Bicyclists; Safety and Human Factors;

Filing Info

• Accession Number: 01992231
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 17-153
• Files: TRB, RIP
• Created Date: Jun 10 2026 11:36AM