The Traffic Simulation And Evaluation Of Merging-area On Freeway

The traffic simulation and evaluation of merging-area on freeway is an important issue about traffic management and control. The reasonable setting is the forefront of the realization of the ramp control of freeway.Based on a plenty of survey data, this paper puts forward the time headway distribution of the main roadway on freeway merging-area and confirms the main distribution of studying on service level of merging-area which comply with negative exponent distribution, 2 rank Erlang distribution, 3 rank Erlang distribution.There are three kinds of condition when vehicles converge to the main lane from ramps: (a) small traffic volume on the main roadway, vehicles converge to the main traffic flow directly. (b) the main roadway contains more traffic volume, vehicles from ramps run and wait for the merging gap to converge. (c) the main roadway contains heavy volume, which close to or exceed the highway capacity , vehicles from ramps keeps waiting and forming queue. Aiming at these conditions, this paper builds up a merging-probability model of the ramp vehicle under different conditions of main roads' volume, as well as a driving distance model and arithmetic on the acceleration lane.Traffic simulation model on merging-area has been built up. It can simulate vehicle merging course in quantities of volume which could not be surveyed easily in China, thus, the system status can be observed conveniently at any time. It can simulate the driving behavior of converging, following, waiting, accelerating in the freeway merging-area. And the vehicle data including velocity, density, queue, delaying time can be acquired. So, the numerical relation of the traffic characteristic and its effective factors can be represented.The applicability of "highway route designing criterion" JTJ011-94 on the suggestion length of acceleration lane is not satisfied with the growing of traffic volume. With the evaluation between the length of accelerating lane and service level of the merging area, the value of accelerating lane length is modified. The propositional length of the accelerating lane is brought forward. The result of the research is significant to guide the geometric design of the merging-area.