Modeling Of Urban Freight Traffic Assignment Based On Trip Chaining

With the tremendous development of modern Logistics, and the requirement of service improvement and reducement of stock for e-commerceand supply chain management of enterprises, the urban freight are towarding the trend of JIT delivery which including multi-product,multi-batchandsmall lot. It promotes the urban freight vehicles increase greatly, which is a disaster for the traffic congestion of metropolitan. Meanwhile, from the freight vehicles’ trip behaviour, it tends to act as a trip chaining which includes more than one trip with the vehicle routing planning level. To make a scientifical and reasonable freight traffic planning has become an urgent action for the freight traffic problems under the situation of modern logistics. In practice, since urban freight traffic planning is a part of the comprehensive traffic planning system, the traffic assignment method is usually the same as the passenger traffic use. However, since the freight traffic is not the same to the passenger traffic in participants, decision-making mechanism, production mechanism and assignment principle, the method suitable for passenger traffic can’t reflect the situation of freight traffic. Meanwhile, the existing methods ignore the relationship between each trip, which is not accorded with the fact that freight vehicles are tend to finish transportation activities using trip chain including much activities from the aspect of trip behavior. So, to more precise reflecting the actual freight traffic situation, the freight traffic assignment model must combine with the factors including production mechanism, characteristics, route choice basis, freight trip behavior and etc.Combined with trip training theory, this paper analyses the freight trip chaining fitted for freight trip behavior and its characteristic indexs, summarizes the different freight trip chaining modes and its influencing factors. Then commodity-based and vehicle-based urban freight traffic demand methods are contrasted, and commodity-based urban freight traffic demand method is choosed to be the basic method. Meanwhile, the traditional traffic assignment models are contrasted to choose the Fisk as the basic model. Then the method of obtaining the freight traffic distribution OD is studied combining with tripchaining theory. With the theory of trip chaining, the principle of minimum general cost, an urban freight traffic assignment model based on trip chaining theory is put forward on the base of Fisk model. Then, the paper puts forward the algorithm for the solution of the right modelwhich is proved available by a simple example. However, the model was put forward on the base of Fisk model, it needs to list the path relate to the trip chain, which is hard for the large network, so that he model of urban freight traffic assignment based on trip chaining is only useful for a network which is not very large.Finally, the approved model and method was used to obtain the freight traffic assignment result for the case of freight traffic planning of Deyang. Then some measures to improve freight traffic network was approved combined with the forcasting result.