Field Testing and Implementation of Dilemma Zone Protection and Signal Coordination at Closely-Spaced High-Speed Intersections

The report presents the details of a study carried out to test and implement a dilemma zone protection technique at three high-speed closely-spaced intersections on Roosevelt Boulevard in Middletown, Ohio. Several factors that affect the testing and implementation of the dilemma zone reduction technique were considered as follows: (a) length of dilemma zone, which allowed for vehicular speeds ranging from 45 mph (72.41 kph) to 60 mph (96.54 kph) since speeds on these roadways are not uniform and tend to vary within a wide range; (b) detectors, which takes into account the varying speeds that exist on these roadways, were located at 300 ft (91.44 m) or 600 ft (182.88 m), but not both; (c) green extensions, which varied from 1 sec to 5 sec in increments of 1 sec, with the "no green extension" being used as the base case; and (d) vehicle conflicts caused by (i) running red light, (ii) stopping abruptly or (iii) accelerating through yellow representing the dilemma zone problem. The traffic data were collected during off peak hours in the morning (9am-11am) and at night (8pm-10pm). In all, 288 hours of data were collected on the six intersection approaches. The analysis revealed that accelerating through yellow was the major conflict for all intersections, followed by running red and stopping abruptly, respectively. The study indicated that the three types of conflicts, namely, running red light, stopping abruptly and accelerating through yellow, can be successfully used to identify vehicles that experience dilemma zone problems at signalized intersections. Overall, this study has shown that, for the roadway segment of Roosevelt Boulevard between Highland and Armco, which has a speed limit of 45 mph (72.41 kph), dillemma zone protection can be effective by placing detectors at 300 ft (91.44 m) and providing a green extension of 3 sec on most, but not all, approaches. The effectiveness was more evident during the morning period than during the night period indicating that drivers' speed behavior may be different during daylight and night conditions. The study shows that there is no one "universal" rule for dilemma zone protection that would apply equally to all intersections because each intersection is unique in its geometric and operational characteristics and vehicular speeds on any intersection varies within a wide range. Recommendations for implementing the technique for future improvements of intersections identified with dilemma zone problems were made.


  • English

Media Info

  • Media Type: Web
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 91p

Subject/Index Terms

Filing Info

  • Accession Number: 01001462
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/OH-2005/006
  • Contract Numbers: State Job No. 14754(0)
  • Created Date: Jun 27 2005 2:15PM