Study On Traffic Flow Parameters At Signal Intersections

As the switching node for urban road traffic flow, the intersection plays an important role in road network system, and the ability for dredging the traffic flow of intersection restrains the operating efficiency of urban road network to a large extent. In recent years, the urban traffic congestion-prone have mostly occurred on intersection nodes. The reason is that the foreign achievements are generally adopted for the traffic control system and the traffic simulation system in our country, there are many traffic flow parameters which are not in conformity with the actual situation of our country and the parameters need to be defined in these systems. When the parameter is not properly, it will reduce the adaptability of the simulation and signal timing. The vehicle arrival time interval of signalized intersection, as well as the departure headway and start-lost time of lining up vehicles are the important parameters having influence on signal timing dial design, intersection traffic capacity and traffic simulation, and analysis of these parameters is one of the means to improve the accuracy of signal control and traffic simulation.This article takes vehicle arrival time interval of signalized intersection as well as the headway and start-lost time of straight flow during lining up vehicle departure as the research emphasis. Firstly, based on field research, the article conducts fitting of distribution on vehicle arrival time interval by utilizing 7 kinds of distribution functions including HErD, normal distribution, lognormal distribution, negative exponential distribution, shifted negative exponential distribution, gamma distribution and weibull distribution. By making comparisons of goodness of fit using coefficient of determin, the conclusion of HErD has preferable fitting result on vehicle arrival time interval is obtained and verified, and the measured data on the intersection of Zhuhai verifies the universality and applicability of the conclusion.Secondly, this article conducts analysis on the headway distribution form of direct movement traffic flow on signalized intersection, and discovers that the departure headway of lining up traffic flow of direct movement can be depicted with lognormal distribution. Besides, this article conducts research on the saturation headway and the start-lost time, this essay thinks the actual measurement of the saturation headway of direct movement traffic flow can be observed from the 4th vehicle, and over in 8th vehicle. Finally, this paper compares the capacity of the saturation volume rate model, stop line method,urban road design criterion stop line method and measured traffic capacity, and draws the following conclusions:(1) As for the approaches with multiple specially purposed direct movement lanes, the average saturation headway of the kerb lane is larger than that of the inside lane, and the capacity of the kerb lane lower than inside lane about 10-20 pcu/h;(2) Two-way left turn waiting zone has significant influence on the saturation flow rate of the fast direct movement lane, which brings influence on the traffic capacity of the fast direct movement lane, It’s capacity lower than the other lanes about 35 pcu/h;(3) The number of specially purposed direct movement lanes has significant influence on the lost time, the start-lost time of specially purposed direct movement lanes in sample data is about 2.7544s. There is large difference with the start-lost time recommended value 1.0-2.0s specified in HCM2010;(4) In the calculation method of capacity (include saturation volume rate model, stop line method and urban road design criterion), the best method is to urban road design criterion.