Dilemma Zone Protection And Signal Coordination At Closely Spaced High Speed Intersections
Download Dilemma Zone Protection And Signal Coordination At Closely Spaced High Speed Intersections PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Dilemma Zone Protection And Signal Coordination At Closely Spaced High Speed Intersections book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages.
Dilemma Zone Protection and Signal Coordination at Closely-spaced High-speed Intersections
A feasibility study of dilemma zone problems, performed by collecting and analyzing traffic flow data at a high-speed signalized intersection, showed that the maximum green extension or cutback needed to get a vehicle out of the dilemma zone is generally no more than 2 seconds. If we scan all vehicles on a link just a few seconds before the beginning of a yellow interval, we may be able to extend or cut back the green interval so that the vehicles can avoid the dilemma zone. For each vehicle approaching an intersection on the link that is about to turn yellow, there is a time interval such that (a) the vehicle will be in the dilemma zone without green extension (or cutback) or (b) it will be in the dilemma zone when there are T seconds of extension (or cutback). So the task is to find the smallest nonnegative integer T that is not in any of these time intervals and extend (or cut back) the current interval by T seconds. This T can always be found and assuming there are no other restrictions, dilemma zones can be avoided and the extension (or cutback) is done at most once for each green interval. The simulation study, performed by modifying the source codes of NETSIM, showed that the signal timing generated by a bandwidth maximization program (PASSER-II) resulted in a lower number of vehicles in the dilemma zone than that generated by a delay minimization program (TRANSYT-7F). Additionally, the signal timing generated by the combination of the two programs, that is, by minimizing delay within the constraint of bandwidth maximization, resulted in an even lower number of vehicles in the dilemma zone than those generated by each program alone. The technique developed in this study can be implemented if the speeds and positions of all vehicles on the roadway can be recorded at small time intervals (e.g., 1 sec). Recommendations are made for implementing and testing the developed technique.
Dilemma Zone Protection and Signal Coordination at Closely-spaced High-speed Intersections
A feasibility study of dilemma zone problems, performed by collecting and analyzing traffic flow data at a high-speed signalized intersection, showed that the maximum green extension or cutback needed to get a vehicle out of the dilemma zone is generally no more than two seconds. Scanning all vehicles on a link just seconds before the beginning of a yellow interval may extend or cut back the green interval so that vehicles can avoid the dilemma zone. For each vehicle approaching an intersection on a link about to turn yellow there is a time interval that (a) the vehicle will be in dilemma zone without green extension (or cutback) or (b) it will be in dilemma zone when there is T seconds of extension (or cutback). The task becomes to find the smallest nonnegative integer T that is not in any of these time intervals and extend or cutback the current interval by T seconds. This T can always be found and assuming there are no other restrictions, dilemma zones can be avoided and the extension or cutback is done at most once for each green interval. The simulation study, performed by modifying the source codes of NETSIM, showed that the signal timing generated by a bandwidth maximization program (PASSER II) resulted in a lower number of vehicles in dilemma zone than that generated by a delay minimization program (TRANSYT-7F). Additionally, the signal timing generated by the combination of the two programs, that is, by minimizing delay within the constraint of bandwidth maximization, resulted in even lower number of vehicles in dilemma zone than those generated by each program alone. The technique developed in this study can be implemented if the speeds and positions of all vehicles in the roadway can be recorded at small time intervals (e.g., 1 sec.). Recommendations are made for implementing and testing the developed technique.
Field Testing and Implementation of Dilemma Zone Protection and Signal Coordination at Closely-spaced High-speed Intersections
Historically, high speed signalized intersections have reported many crashes and have always posed a challenge to traffic engineers for enhancing safety at these intersections. The area close to the intersection, called the dilemma zone, poses a high accident potential for the driver in stopping safely during the yellow interval or in proceeding through the intersection before the beginning of red. The driver is in a potentially hazardous situation whereby, if he tries to cross the intersection at the onset of red interval, he may end up in an angle accident with the cross street traffic or if he accelerates through yellow, he may end up in a rear-end collision. The uncertain situation in a dilemma zone can potentially lead to rear-end or right angle collisions.