Land use planning of big traffic generators: the need for new tools

1. Abstract We present a mathematical model based decision support system for the placement of big traffic generators (BTG) like shopping centres. The model aims to forecast the traffic flows induced by BTG on the road network of Canton Ticino in Switzerland, and is beginning to be used by the public administration as a support to decide master plan rules for zones selected for the reception of BTG. In general, it can also be used for the planning of placement or rejection of new projects of BTG. The system has been modelled as an Interaction Space, a new type of mathematical structure generalizing both multiagents systems and cellular automata and aiming to axiomatically define complex systems made by several interacting entities. The presented model use methods more near to the way of thinking of Physics, like the use of populations of individuals, but with several positive elements inherited from multi-agents systems. Indeed, we can say that the model is an activity-based modelling of the whole private transportation system of Canton Ticino, but with the use of populations of agents instead of individual agents. Fuzzy logic based methods, instead of the classical random utility theory, have been used to define several indicators, both to model agents’ behaviour or attractiveness indicators for zones containing economical activities. The use of these indicators permits to obtain agents’ location choices of secondary activities with a great and scalable computational efficiency. Suitably organized simulations obtained from the model include several environmental indicators, and can be used to support decisions in the placement of new BTG or in the definition of areas intended to receive BTG. A partially incomplete, but anyhow meaningful, version of the model has also been used to test a classical planning strategy consisting in the imposing of a maximum level of commercial surface suitable for BTG in a prefixed number of zones (called divisions). We performed a suitable simulation where every division has been filled uniformly in time until to arrive at its filling, with the aim to forecast the situation of worst environmental impact caused by BTG located in divisions. Some final results of this simulation has been unexpected, like the decreasing of NO x in some points (but not all) with respect to the present situation. This underline the need for new planning strategies in the displacement of BTG.