2.5 Traffic Flow between Intersections Assuming Structured Platoons

Transcription

1 2.5 Taffic Flow between Intesections Assumin Stuctued Platoons A time-space diaam (TSD) can be used to epesent vehicle flow on an ateial between sinalized intesections. The TSD shows the tajectoy of vehicles tavelin alon the ateial usin both the time and distance domains. Fiue 1 shows a well-stuctued platoon of six vehicles tavelin thouh two sinalized intesections at constant speed and with unifom headways, aivin duin een at both intesections. The vehicles expeience no delay. Fiue 1 also shows seveal aspects of the sinal contol system. The cycle lenth is the sum of the een, yellow, and ed intevals fo one phase. The offset at the second sinalized intesection is the diffeence between the stat of een at the fist intesection elative to the stat of een fo the second intesection. Cycle lenth, C Offset Fiue 1 Time space diaam CE 474 Fall

2 A simplified vesion of this same TSD is shown in Fiue 2. Hee the displayed een (), yellow (Y), and ed () intevals ae eplaced by the effective een () and effective ed peiods (). Also, only the fist and last vehicles in the platoon ae shown. In both fiues, the platoon is assumed to be well-stuctued as all vehicles tavel at the same speed with unifom headways between each vehicle pai. In addition, Fiue 2 shows the bandwidth, defined to be the maximum time duation of the platoon that can be seved with the een band povided alon the ateial. Cycle lenth, C Offset Bandwidth Fiue 2 Time space diaam CE 474 Fall

3 Fiue 3 shows the case whee all vehicles aive at the second intesection duin the ed inteval. Fiue 3 Time space diaam, aivals on ed at downsteam intesection CE 474 Fall

4 Fiue 4 shows the same case, this time with an inveted QAP shown with a dashed line. The queue ows duin ed duin the aival of the six vehicles, it emains steady afte the sixth vehicle aives, and beins to clea afte the beinnin of een. The shaded aea shown in liht ed is the total delay expeienced by these vehicles. Fiue 4 Time space diaam, aivals on ed at downsteam intesection, queue accumulation polyon CE 474 Fall

5 Distance, ft Activity C01: Intesection Spacin, Offset, and Vehicle Speed (Time-Space Diaams) Pupose The pupose of this assinment is to constuct a speadsheet tool that you can use to study the effect of chanin intesection spacin, speed, offsets, cycle lenth, and splits on the quality of poession thouh the intesections of you system. equiements 1. A time-space diaam in an Excel wokbook showin tajectoies fo the font and back of two platoons, one tavelin in one diection and anothe in the opposite diection thouh you system of fou intesections. See the example below that shows a timespace diaam fo two intesections ove a peiod of nealy two cycles. 2. Input data that contol the fou platoon tajectoies and the ed and een sinal display lines ove two cycles in the time-space diaam. 3. A cycle lenth of 100 sec and an effective een time of 50 sec. 4. A platoon duation of 30 sec. 5. An offset of zeo fo the fist (efeence) intesection in you system Time, sec CE 474 Fall

6 Tasks 1. Measue the distance between you intesections usin oole Eath o a simila tool. 2. Constuct the input data space that satisfies equiement Add the time-space diaam includin: The hoizontal lines epesentin the intesections, The een and ed display lines fo each intesection, and The leadin ede of the up platoon, the tailin ede of the up platoon, and the leadin and tailin edes of the down platoon. (Note: The tajectoy lines should espond to any chane in the intesection spacin and vehicle speed. The sinal display lines should espond to any chane in the intesection spacin, the cycle lenth, the splits, and the offset.) 4. Compute the tavel time between each intesection pai to be used as initial values fo the offsets, assumin the speed limit in each sement is a ood epesentation of the tavel speed. 5. Detemine the best offsets to achieve poession fo the up diection only. Deliveable Excel wokbook with time-space diaam as pe the equiements listed above. CE 474 Fall