Inventory, Operations, and Safety at Free Right-Turn Ramps

Research on right turns at rural intersections on the state highway system was initiated by the Nebraska Department of Transportation (NDOT) during the 1990’s (McCoy et al., 1995) and again during the 2016-2018 period (Khattak and Kang, 2018). In the former study, the authors developed guidelines for the establishment of FRT ramps on rural two-lane highways in Nebraska based on a benefit-cost analysis. They recommended that design-year right-turn AADTs ranging from 440 to 825 vehicles per day (depending on truck percentage) warranted a FRT ramp at unsignalized intersections on rural two-lane highways. Acceleration lanes improved vehicle merge operations and while right-turning traffic moved efficiently, there were no discernable safety improvements from FRT ramps. In the latter study, the authors looked at safety and economic benefits of rural intersections with offset right-turn lanes (ORTL) compared to rural intersections with no right-turn lanes and those with traditional right-turn lanes. They also investigated drivers’ stopping behavior on the minor approaches at ORTLs. Results showed ORTLs had the lowest crash rates; however, the difference was statistically not significant. The cost-benefit analysis indicated that compared to intersections with no right-turn lanes, ORTL intersections had an annual reduction of 0.202 crashes per million entering vehicles, which translated to $22,662 savings in crash costs per year. When compared with intersections having no right-turn lanes, a traditional right-turn lane reduced 0.0758 crashes per million entering vehicles annually or $8,504 savings in crash costs per year. Driver stopping behavior assessment showed that number of through lanes, width of right-turn lane and width of the ORTL offset were statistically associated with driver’s stopping position on the minor approach and overall drivers were taking advantage of the ORTLs improved sight distance. In this study, free right-turn (FRT) ramps were excluded due to their uniqueness (compared to traditional right-turn lanes and ORTLs) for a later study. NDOT has several FRT ramps across the state highway system. The intersection minor approaches stop-controlled and varying driver warning devices may be in place at these locations. There are concerns about the safety and operations of FRT ramps and therefore, there is a need to review the operations and safety of these locations.

Language

• English

Project

• Status: Active
• Funding: $182,563.00
• Sponsor Organizations:

  Nebraska Department of Transportation

  1500 Nebraska 2
  Lincoln, NE  United States  68502
• Project Managers:

  Halsey, Lieska

• Principal Investigators:

  Khattak, Aemal

• Start Date: 20210701
• Expected Completion Date: 20230531
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Crash analysis; Driver education; Operations research; Traffic
• Identifier Terms: Nebraska Department of Transportation
• Subject Areas: Design; Highways; Operations and Traffic Management; Research; Safety and Human Factors;

Filing Info

• Accession Number: 01769369
• Record Type: Research project
• Source Agency: Nebraska Department of Transportation
• Files: RIP, STATEDOT
• Created Date: Apr 12 2021 2:52PM