Capacity Analysis of Traffic-Actuated Intersections Final Report (1996) / Chapter Skim
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APPENDIX A
APPENDIX A
Pages 39-56
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From page 39... ...
Traffic-actuated control definitions, Warrants for traffic-actuated control, Benefits and operating considerations for traffic-actuated control, Effects of coordination and phase-skipping for traffic-actuated control, Late-night, low-volume operation of coordinated actuated systems, Evaluation of traffic-actuated control by simulation, Estimation of green times and cycle length for traffic-actuated control, Delay models for traffic-actuated control, Signalized intersection capacity models for traffic-actuated control, and Overview and evaluation of "Enhancement of the Value Iteration Program for Actuated Signals" (EVIPAS)
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From page 40... ...
, concluding that they provide good guidelines for selecting actuated equipment for locations where traffic volumes do not warrant pretimed signals. The current edition oftheMUTCD stops short of numericalwarrants for choosing between pretimed and traff~c-actuated control, but it does suggest certain qualitative conditions under which trafficactuated control should be implemented.
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From page 41... ...
expanded the body of theory by developing relationships for mean vehicle delay with both Retimed and actuated control at intersections of one-way streets and intersections oftwo-way streets, respectively. In reference 10, Newell demonstrated that the average delay per vehicle for an actuated signal is less than that of a pretimed signal by a factor of about three for intersections of oneway streets.
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From page 42... ...
, at low and moderate volumes when extensions oftwo or three seconds are employed, the use of fit actuated controllers will produce reduced delays and stops over those obtained using pretimed controllers. When high traffic volumes occur on both main and side streets causing the controller to extend the green time to the maximum on all phases, the fi~li-actuated controller wait perform as a pretimed controller, producing comparable measures of vehicle flow.
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From page 43... ...
In 1985, Lin [15] studied the optimal timing settings and detector lengths for full-actuated signals operating in presence mode using the RAPID simulation model.
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They also evaluated the existing signal control parameters on an individual traffic-actuated signal. The significant conclusions are summarized as follows: Under low volumes, the maximum green settings have little or no effect on the performance of actuated signal controllers.
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studied the coordination of actuated arterial traffic signal systems. In the past, all existed optimization methods required that each actuated signal be converted to its nearest equivalent pretimed unit.
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From page 46... ...
investigated the interactions between queuing vehicles and detectors for actuated controls, which govern the initiation, extension, and termination of a green duration. They emphasized that the model used in the simulation analysis should be calibrated in terms of observed characteristics such as queue discharge headway, arrival headway, the relationship between the arrival time of a queuing vehicle and the departure time of its leading vehicle, the number of queuing vehicles in a defined area at the onset of a green duration, and the dwell time of a vehicle on the detection area.
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From page 47... ...
This study provided a good contribution to traffic simulation users, given the large expenditures on computer simulation. ESTIMATION OF GREEN TIMES AND CYCLE LENGTH FOR TRAFFIC-ACTUATED CONTROL Traffic-related phenomena at a signalized intersection, such as lane capacity, delay and queue length are influenced by the phase times and cycle length.
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From page 48... ...
which uses negative exponential or shift negative exponential distribution of arrival headway can be derived as a special case of the bunched arrival mode} through simplifying assumptions about bunching characteristics of the arrival stream. The methods given in his papers provide essential information (average green times and cycle length)
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From page 49... ...
for level-of-serv~ce analysis at signalized intersections. The use of this mode} for the evaluation of traffic-actuated signal operations required a knowledge of the average cycle lengths and green intervals associated with the signal operation being analyzed.
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In chapter 9 of the 1985 HCM, he thought it was not appropriate to treat the pretimed and actuated controls identically, especially concerning the estimation of capacity and performance of existing Intersections. The study verified the fact that intersections with traffic-actuated signal controls demand special treatment when estimating their capacity and performance.
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The signal performance summary table shows the average phase length and average cycle length. All above delay measures, average phase length, and average cycle length are based on the m~crosimulation results.
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Figure AM Phase time comparison between EV1PAS and NETSIM A simple regression analysis between the above two simulated phase times was performed and a 0.96 coefficient of determination, R2, was achieved. As expected, the simulated phase times Dom EV1PAS are very close to those Dom NET SIM simulations.
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From page 53... ...
S Parsonson, llSelecting Traffic Signal Control at Individual Intersections,ll NCHRP Report 233, Transportation Research Board, National Research Council, Washington D.C., June 1981.
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From page 54... ...
G Courage, "Late-N~ght Traffic Signal Control Strategies for Arterial Sys tems," Transportation Research Record 1287, TRB, National Research Council, Washington D.C., 1990-1991, pp.
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From page 55... ...
34. Lin, Feng-Bor, "Estimating Average Cycle Lengths and Green Intervals of Sem~actuated Signal Operations for Level-of-Service Analysis," Transportation Research Record 1287, TRB, National Research Council, Washington D.C., 1990-1991, pp.
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From page 56... ...
R Mekemson, "Comparison of SOAP and NETSIM: Pretimed and Actuated Signal Controls," Transportation Research Record 905, TRB, National Research Council, Washington D.C., ~983-~984, pp.
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