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Unformatted text preview: Lecture 10 Lecture 10 Control of Isolated Traffic Signals Control of Isolated Traffic Signals Profs. Profs. Ismail Chabini Ismail Chabini and and Amedeo Amedeo R. R. Odoni Odoni 1.225 1.225 J (ESD 225) Transportation Flow Systems J (ESD 225) Transportation Flow Systems 1.225, 12/3/02 Lecture 10, Page 2 Lecture 10 Outline Lecture 10 Outline Isolated saturated intersections Definitions: Saturation flow rate, effective green, and lost time Notation for an intersection approach variable Two assumptions for delay models Average delay per vehicle: deterministic term W q,A Average delay per vehicle: stochastic term W q,B Webster optimal green time settings: two approaches intersection and numerical example Webster cycle time optimization procedure Midday and eveningpeak examples Lecture summary 1 1.225, 12/3/02 Lecture 10, Page 3 Isolated Saturated Intersections Isolated Saturated Intersections q E q W q S q N P 2 q Average arrival rate at an approach Average departure rate from an approach P 1 Saturation regime for P 1 An implication of saturation regime: need to efficiently allocate green times ( g N , g S ) and ( g E , g W ) Saturation regime for P 2 1.225, 12/3/02 Lecture 10, Page 4 Saturation Flow, Effective Green, and Lost Time Saturation Flow, Effective Green, and Lost Time Green ( k ) Amber ( a ) Red Red Effective green time ( g ) Lost time ( l 2 ) Lost time ( l 1 ) Time Rate of discharge of queue in fullysaturated green periods Total lost time l = l 1 + l 2 (typically 2 sec) Green ( k ) + Amber ( a ) = Effective green time ( g ) + Total lost time ( l ) l = k + a  g Effective green time ( g ) u Saturation flow ( s ) = Total vehicles discharged during ( k + a ) Saturation flow s 2 1.225, 12/3/02 Lecture 10, Page 5 Notations for An Intersection Approach Notations for An Intersection Approach Webster time cycle in...
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This note was uploaded on 12/06/2011 for the course ESD 1.225j taught by Professor Ismailchabini during the Fall '02 term at MIT.
 Fall '02
 IsmailChabini

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