01152735

Component

This paper examines the effects of truck percentages on start-up lost times at a signalized intersection because of their effects on saturation flow rates and vehicle headways. Start-up lost time is typically defined as the difference between the time used by the first four vehicles in the queue to clear the stop line when the light turns green versus the time they would have taken at the average saturation headway for that lane group of the intersection. The 2000 Highway Capacity Manual procedures do not adjust lost times for truck percentages specified by the user even though higher truck percentages should result in higher lost times since trucks start moving more slowly at the beginning of the green phase. New methods of calculating and estimating start-up lost times as affected by truck percentages in the vehicle mix are presented. The new field calculation method also reduces the frequency of finding negative lost times in field observations if there are trucks or slowly moving vehicles in the queue after the first four vehicles. Four cases are analyzed where trucks may be present among vehicles 1-4 and/or vehicles 5-n of a queue at a red light. According to our field observations, the mean start-up lost time was higher when trucks were in the queue and highest when trucks were among both vehicles 1-4 and 5-n of the queue. We recommend a method to estimate start-up lost time in the Highway Capacity Manual 2000 procedures to adjust for the truck percentage specified by the user.

01147878

10-0412

English

14p

2010

Transportation Research Board 89th Annual Meeting

DVD

Figures; Photos; References (8) ; Tables (10)

Green interval (Traffic signal cycle); Highway operations; Signalized intersections; Starting (Driving); Truck traffic; Trucking

Start-up lost time

Highways; Operations and Traffic Management; I73: Traffic Control

Transportation Research Board Annual Meeting 2010 Paper #10-0412

TRIS, TRB

Jan 25 2010 10:14AM