ALBERT GROVER & ASSOC. 1 -2003 - Laserfiche WebLink

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Mr. Dowling Tsai January 10, 2003 Page 6 coordination analysis while both SYNCHRO and TRANSYT provide system-wide delay minimization, ~vhich is not always compatible with overall objectives. The following discussion is based on the premise that optimization of arterial progression is the primary goal of this coordination timing project. For this project, AGA proposes to utilize SYNCHRO in addition to PASSER (a grid arterial progression program), TRANSYT and WEBSTER (signal timing optimization program) in an interactive manner. Cycle Length and Timing Analysis: The system cycle length determination is extremely critical, as the cycle length must be minimal to achieve maximum benefits. AGA will identify critical .intersections and perform detailed capacity/delay analyses using sophisticated delay optimization routines to help establish system/subsystem cycle lengths. When system cycle lengths are arbitrarily selected rather than minimized and optimized, complaints often arise from local side street traffic because of their increased ~vaiting time. The PASSER and WEBSTER programs will be used to help calculate the signal timing information including cycle lenZhs, splits, phase sequences and offsets for signalized intersections along the project routes to maximize arterial progression and to reduce delay~' The different traffic flow conditions, including various assumptions relative to potential non- recurrent incident locations and resultant traffic volume variabilities, will be analyzed and timing plans ~vill be developed accordingly. WEBSTER, which was developed by Mr. A1 Grover based on the HCM2000, allows an engineer to quickly analyze each intersection independently to determine the minimum delay, cycle length and queuing for each one. WEBSTER considers pedestrian minimum times, overlap phasing and left mm minimums. This analysis results in different cycles for most intersections, which can then be logically grouped into subsystems with common cycles. This process results in optimum coordination timing grouping while minimizing side street delay. The optimization will include the analysis of progression based on optimum phase sequences (leading lefts, lead/lag, etc.) selected by the PASSER program to provide the best arterial progression. The results of the progression analysis will be shoWn on time-space diagrams. The TRANSYT program will be used to evaluate queue lengths, stops and delays resulting from the impacts/benefits of coordination. We only use TRANSYT after we conduct a very detailed and careful evaluation of the entire system to identify a proper cycle length for each time period. Anyone can use the tools (PASSER, TRANSYT, SYNCHRO and WEBSTER), but good results require a very experienced team. AGA timing experts do not simply proceed with the computer timing outputs from these tools, but carefully review the program output and adjust the values manually, using time-space diagrams, to properly match local conditions. Lead/Lag Phasing: Another factor that will influerfee the development of coordination timing plans for the project arterials involves lead/lag phasing at protected left turn