trans_sys_chap26

trans_sys_chap26 - time spent stopped at red lights for...

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Introduction to Transportation Systems 1
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PART III: TRAVELER TRANSPORTATION 2
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Chapter 26: Traffic Signals and Other Control Measures 3
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Traffic Light Synchronization Space-Time Diagram distance C B A offset offset Green Band Green Red slope = velocity time Cycle The slope of the line defining the green band is speed (the ratio of distance to time). If a car stays within that green band as it goes through traffic signals A, B and C, it will continue unopposed by a red light. Figure 26.1 4
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Grid Network D B C A ± We consider the design of “splits” -- dividing the total cycle time (the time between the start of consecutive reds) between the red and green. ± We consider “offsets” -- the time between light A and light B turning green. ± The question is how to design the splits and the offsets in the two directions optimally. 5 Figure 26.2
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Optimizing Traffic Light Settings But what is optimal? ± One might consider the total amount of
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Unformatted text preview: time spent stopped at red lights for vehicles in the system, considering both directions. ± An alternative measure is the number of times that individual vehicles need to stop. ± Simply optimizing the total time in the system is another approach. 6 Traffic Light Synchronization -- Levels of Sophistication The “Minus-One” Alternative --Mystic Valley Parkway, Medford, MA, U.S. Street Sign 7 Figure 26.3 Traffic Light Synchronization -- Levels of Sophistication: 2 ± Static Synchronization ± Time-of-Day Settings ± Pre-Defined Plans ± Dynamic Systems 8 Other Traffic Control Ideas ± Ramp Metering ± Dedicated Bus Lanes ± Reversible Lanes ± High-Occupancy Vehicle Lanes ± High-Occupancy Toll Lanes ± Traffic Calming 9 CLASS DISCUSSION ± Use of these various ideas in your city? Issues: ± Do they work? ± Public acceptance? ± Who gains and who loses? 10...
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This note was uploaded on 12/06/2011 for the course ESD 1.221j taught by Professor Josephsussman during the Fall '04 term at MIT.

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trans_sys_chap26 - time spent stopped at red lights for...

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