Developing Sight Distance Guidelines for U-Turn Maneuvers

Details

• Creators:
  Tsai, Yichang (James) ; Agnihotri, Atharv ; Huang, Zhijing ; O’Brien, Scott R. ; Balla, Venkateshwarlu ; Yang, Zhongyu
• Corporate Creators:
  Georgia Institute of Technology
• Corporate Contributors:
  Georgia. Department of Transportation. Office of Performance-Based Management & Research ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  AASHTO Crash Data Guidelines Intersection Design Intersections Maneuvering Medians Median Width Performance Restricted Crossing U Turn Intersections Sight Distance Traffic Crashes U-Turn Sight Distance Vehicle Maneuver

  More +
• Publication/ Report Number:
  FHWA-GA-26-2303
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report (January 2024 – January 2026)
• Corporate Publisher:
  Georgia. Department of Transportation. Office of Performance-Based Management & Research
• Abstract:
  This project, conducted by the Georgia Tech research team in collaboration with the Georgia Department of Transportation (GDOT), aims to develop safe and practical U-turn sight distance (UTSD) guidelines for Reduced Conflict U-turn (RCUT) intersections. The research analyzed video footage from GDOT to quantify U-turn maneuver times under varying median widths and incorporated these observations into sight distance modeling. Results showed that vehicles at wider median noses, where they have storage in the median to position themselves perpendicular to traffic and make a 90 degree turn, completed U-turns in approximately 4.25 seconds; while for narrower median noses, where vehicles can’t position themselves perpendicular to traffic and take a 180 degree turn, the u-turning time increased to about 5.8 seconds. These empirical values were integrated with acceleration distance needed to reach 70% of the design speed to derive UTSD using the basic intersection sight distance equation. The resulting UTSD tables provide design guidance across different median widths and design speeds, ensuring adequate time and space for safe U-turn maneuvers. An accompanying Excel tool was also developed to facilitate practical application of the model. Comparisons against models from Florida DOT, Louisiana DOTD (AASHTO case F) and other AASHTO cases demonstrated that the proposed model achieves a balanced level of conservatism and feasibility. Furthermore, crash data analysis from selected RCUT sites confirmed the model’s capability to identify locations with insufficient sight distance, supporting its potential to enhance intersection safety and operational performance.
• Format:
  PDF
• Funding:
  PI# 0019905
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:3e3fba53a02ed78fc60cb2d567ea86038387b3fee167febf8191c801775c8c3ee5a86644c3f43183e2627da1c51cffe5c047d566652298e0e9665b7e16e8f6b0
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/88890/dot_88890_DS1.pdf
• File Type:
  [PDF - 1.68 MB ]