Sustainable urban transportation development: a modelling approach

摘要

Transportation networks are complex systems and the study of their efficient operation, often through some outside intervention, has attracted much interest from transportation professionals. This increased interest for mobility and accessibility options in the framework of sustainable development inspired the authors to develop a quantitative approach for internalising sustainability constraints in a transportation planning context. Some preliminary results are discussed in this paper. First, some conceptual ideas on sustainable urban transportation development are presented as well as the general structure of a dynamic optimisation model. This model characterizes the changing states of system capacity and allowable traffic volume as a result of investment in infrastructure (like construction and maintenance). The constraints in the model represent the resource capacities derived from the principles of sustainable development (for example financial and environmental sustainability). The travel demand is assumed to be partially elastic to the state of the system. Second, the optimal control solution to the problem is derived and discussed for a sample transportation network. The model thus reveals what steps ought to be taken, when and where, and by how much in order to achieve sustainability targets. It is then concluded that a dynamic approach to modelling sustainable urban transportation development is intrinsic to the nature of the problem. Transportation systems always operate in a partial dis-equilibrium, and hence models that are able to deal with this lagged - adjustment and resource constraints should be developed. The operational feasibility of this kind of models is evident. However, development of large-scale dynamic models like the one proposed here still poses some computational challenges.