Evaluation of j-turn intersection design performance in Missouri.

Details

• Creators:
  Edara, Praveen ; Sun, Carlos ; Breslow, Sawyer
• Corporate Creators:
  University of Missouri--Columbia. Dept. of Civil Engineering
• Corporate Contributors:
  United States. Federal Highway Administration ; United States. Department of Transportation. Research and Innovative Technology Administration ; Mid-America Transportation Center
• Subject/TRT Terms:
  At Grade Intersections Before And After Studies Crash Analysis Crash Rates Crash Severity Field Studies Highway Design Rural Highways Surveys Traffic Crashes Turning Traffic

  More +
• Publication/ Report Number:
  cmr 14-005
• Resource Type:
  Tech Report
• Geographical Coverage:
  Missouri
• Corporate Publisher:
  Missouri. Dept. of Transportation. Organizational Results
• Abstract:
  Research shows that a high percentage of crashes that take place on high-speed rural expressways occur at intersections with
  
  minor roads. One low-cost alternative design for improving the safety of at-grade intersections on such expressways is the J-turn.
  
  In the last few years, the Missouri Department of Transportation has converted some two-way stop controlled (TWSC)
  
  intersections into J-turns. This study evaluated the effectiveness of the J-turn intersection design in Missouri utilizing field
  
  studies, a public survey, crash analysis, and traffic conflict analysis. The field studies collected detailed video data at a J-turn site
  
  and a control site. The crash analysis included a statistically rigorous empirical Bayes before-after safety evaluation of five J-turn
  
  sites in Missouri. The J-turn design resulted in a 34.8% reduction in crash frequency for all crashes and a 53.7% reduction in
  
  crash frequency for all injury and fatal crashes. Both reductions were significant at the 95% confidence level. Annual disabling
  
  injury crashes and minor injury crashes decreased by 86% and 50%, respectively. None of the five sites exhibited a fatal crash
  
  following J-turn implementation. This five-site analysis showed that annual right angle crashes decreased from 6.3 to 1.3, a 80%
  
  reduction. One of the most severe crash types, the left turn, right angle crash, was completely eliminated by the J-turn. One
  
  conflict measure, average time to collision, was found to be four times higher at the J-turn site compared to the control TWSC site
  
  among minor road turning vehicles, indicating greater safety at the J-turn site. The average wait time at the J-turn site was half the
  
  wait time at the control site, while the average travel time at the J-turn site was approximately one minute greater than at the
  
  TWSC site. When the public was surveyed regarding trip time perceptions resulting from the J-turn, the majority said there was
  
  no adverse effect. A high percentage of minor road left turning and through movements at the J-turn site merged into the travel
  
  lanes within the first 400 feet of the acceleration lane. Public opinion regarding the J-turn at US 63 and Deer Park Rd was mixed.
  
  Frequent concerns raised by respondents included difficulty merging following the U-turn, improper use of acceleration and
  
  deceleration lanes, insufficient U-turn radius to accommodate large vehicles, and driver confusion.
  
  
• Format:
  PDF
• Funding:
  TRyy1304
• Collection(s):
  University Transportation Centers US Transportation Collection
• Main Document Checksum:
  urn:sha-512:a04107c2002772ab9396862c4747722de5c4557cde6aaf4d87264d19bd91c65c78e83a2b1532f8783d53dbd28f61e23dccef3433a74de6e04f2b37668d67c3da
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/26829/dot_26829_DS1.pdf
• File Type:
  [PDF - 1.84 MB ]