Impact Of Downstream Stretching-segment On Capacity Of Signalized Intersection

It could exist that the lanes of downstream is less than through lanes of upstream on the construction. Several short lanesshould be built to match the number of through lanes in the downstream,those short lanes are called downstream stretching-segments. Currently,downstream stretching-segments have been frequently used in many cities in China,however, there are still no well-established criteria on their design and use, which has led many questions.To help address the issue, this paper puts forward theimpact of downstream stretching-segment and its main influence factors, and then explores them by field investigation and simulation study.In the field investigation, this paper takes the method of comparative analysis. Three kinds of intersections are taken into survey. One is three through lanes in upstream and three lanes in downstream, one is threethrough lanes in upstream and two lanes in downstream, another is threethrough lanes in upstream but have two lanes and one short lanes in downstream. The saturation flows of three different categories of intersections are compared.In the simulation study,this paper uses the VISSIM simulation software and explores the influence of downstream stretching-segment on the capacityof signalized intersections and its main influence factors. And thenthe relationships among capacity, green timeand the length of short laneare studied on the basis of the simulation’s data.Conclusions are made in this paper as follows:(1)The capacity of intersection with downstream stretching-segment cannot be calculated as the HCM 2000.Because the HCM2000 overestimated the capacity.(2)Compared with the three-lane-to-two-lane intersection, the downstream stretching-segment could improve the capacity of intersection.(3)The capacity of through lanes in signalized intersectionsispositively linked with the length of the short lane of the downstream stretching-segment,and the increasing speed is lower and lower. (4)The capacity of through lanes in signalized intersectionsis negatively correlated to green time, and its decreasing speed is lower and lower.