MIT1_258JS10_lec23

MIT1_258JS10_lec23 - Transit Transit Signal Priority Peter...

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ransit Signal Priority Transit Signal Priority Peter G. Furth Northeastern University
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ransit Signal Priority Transit Signal Priority – elp or Hype? Help or Hype? • Zurich: nearly zero traffic delay for trams, en with mixed traffic (and punctuality!!) even with mixed traffic (and punctuality!!) San Diego trolley: green wave through downtown intersections •Som e US a pplications: < 3 s savings per intersection , or … o measurement at all No measurement at all 2
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ransit Priority as a Societal Transit Priority as a Societal bjective Objective ransit use benefits society in terms of Transit use benefits society in terms of – Congestion – Air quality, climate impact, energy use – Vibrant communities • Priority breaks the vicious cycle in which ngestion drives people to switch from congestion drives people to switch from transit to car 3
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Priority Makes Sense One extreme ($$$$): build a metro ther extreme: do nothing, buses become do nothing, buses become Other extreme: swamped in congestion raffic delay can represent 30% of a bus route’s Traffic delay can represent 30% of a bus route operating cost – Feeds vicious cycle of ever-lower transit use In between: riority in space: Priority in space: bus lanes etc bus lanes, etc. – Priority in time: signal priority 4
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hat Priority Means to a Transit What Priority Means to a Transit peration Operation Reduced running time ($$, passenger benefit). Measures: Delay per intersection Average route running time Improved reliability ($$, passenger benefit). – Recovery time, cycle time based on 95-percentile running time – Tri-Met Line 12: reduced needed cycle length from 104 min to 93 min (11%) 5
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Operational Control: Schedule Adherence, Crowding chedule deviation along the Schedule deviation along the route, without priority, With priority indhoven Eindhoven 6
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Priority Makes Transit … • More competitive – Bus has natural disadvantages due to stops and walking / waiting – Priority compensates, especially if cars suffer ngestion congestion • More socially acceptable (red carpet) – my great aunt … 7
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Intelligent Signal Priority • Not “preemption” (too blunt) • Not “cautious priority” (almost useless) telligent tactics algorithms detection to Intelligent tactics, algorithms, detection to give transit near-zero-delay service, without undue impact on other traffic 8
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9 reen Extension Green Extension • Built-in logic in modern controllers •L a r g e benefit to a few buses – Therefore little disruption to traffic • Extension increment is a parameter (10 s? 15 s?) Without priority With green extension um ulative cumulative cumulative vehicles bus delay bus d e lay v s 1 1 1 s v 1 red green time tim e X norm al
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“Priority Push” is not the same as Allowed Extension ithout priority Without priority ith green extension With green extension cumulative vehicles bus delay v s 1 1 1 s v 1 red green time tim e X norm al R 2 1 R 2 1 X R X 2 (1 v s ) E [ delay ] E [ delay ] = = 2 C 1 s v C 2
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This note was uploaded on 12/06/2011 for the course ESD 11.380j taught by Professor Fredsalvucci during the Fall '02 term at MIT.

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MIT1_258JS10_lec23 - Transit Transit Signal Priority Peter...

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