Rationalisation of urban freight transport systems considering environmental impacts

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This paper deals with the concept of city logistics that is proposed to rationalise the urban freight transport. This paper presents modelling the vehicle routing and scheduling with time windows, the heuristic approach for the problem and the integrated model with dynamic traffic simulation that are essential in city logistics initiatives. These models were applied to a road network to evaluate the impacts on costs, environment and traffic congestion by city logistics initiatives.A model was formulated for the vehicle routing and scheduling problems with time windows (VRPTW) for minimising the total costs. This type of model is at NP-hard level. It is hard to identify the exact solution of the problems. Three heuristic methods, genetic algorithms, simulated annealing and tabu search were applied. After applying these three methods for VRPTW, results showed all three methods provide good approximate solution within the short calculation time.A combined model of VRPTW and dynamic traffic simulation was developed. This model incorporates the interaction between the optimal planning of VRPTW by freight carriers and the traffic condition on road network. The model was applied to a test network. Results indicated that advanced vehicle routing and scheduling planning, co-operation and load factor controls can contribute to alleviate traffic congestion and improve environment as well as reduce costs. The co-operation for carrying goods can be effective to keep COィイD22ィエD2 emissions by trucks at the same level even if the freight demand was doubled. Therefore these initiatives are very promising for realising city logistics.