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 accommodating 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 and bicyclists, though active transportation activity was generally limited because fewer nearby destinations existed. As development intensifies, pedestrian and bicycle activity increases alongside turning conflicts, creating pressure on agencies to widen the roadway cross-section by adding center turn lanes, bicycle lanes, sidewalks, or shared-use paths. While active transportation users benefit from dedicated facilities, they may not benefit from roadway changes that increase vehicle speeds, traffic volumes, or unprotected crossing distances. Meanwhile, motorists on two-lane roadways with frequent left-turning vehicles may experience more rear-end crashes, driver frustration, and risky drive-around maneuvers. Drivers making left turns under these conditions may also accept smaller traffic gaps or perform less thorough scans for pedestrians and bicyclists. When agencies determine that adding pedestrian and bicycle facilities alone is insufficient to meet operational needs, an important question remains: how can transportation agencies improve traffic operations while optimizing safety for active transportation users? 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 bicycle lanes, sidewalks, and effective pedestrian crossing treatments. The research will identify the traffic, land use, and operational conditions under which each cross-section is more effective at improving pedestrian and bicyclist safety 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:

  National Cooperative Highway Research Program

  Transportation Research Board
  500 Fifth Street, NW
  Washington, DC  United States  20001

  American Association of State Highway and 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
• Project Managers:

  Deng, Zuxuan

• Start Date: 20260608
• 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