Applications of Decision Support Systems to Environmental Impact Evaluation of Road Transport Infrastructures

This paper discusses Decision Support Systems for Environmental Impact Assessment of road transport infrastructures. Points to follow in practical applications are described, and key features of the impact analysis phase and decision phase are illustrated making reference to two case studies, the Pedemontana highway in Lombardy and Mantua ring-road. These case studies were carried out by means of SILVIA, a specific Decision Support System to manage the different phases of an Environmental Impact Assessment. The EIA as a decision process Public decisions regarding transport infrastructures, which produce a major environmental, social, and territorial impact, can be facilitated by Environmental Impact Assessment (EIA) (Lee, 1983; Clark, et al., 1984; Commission of the European Communities, 1993). In most countries, this is explicitly required by legislation. EIA is not a technique but a decisional procedure, which possibly makes use of different techniques. The underlying logic is that of Decision Support Systems (DSSs): give all the necessary information to the decision maker, and eliminate successively all the alternatives which are certainly "bad", because they are Pareto dominated or too conflicting, or because they have critical impacts on some sector. This allows both to reduce progressively the dimensions of the problem and to better define the significant characteristics of the remaining alternatives, making the actual entity of the existing conflicts clear. The final decision is in any case political, but the procedure leading to it can be made rational and transparent. A decision process exists only if there's a choice among different alternatives. The alternatives are at least two: to carry out a project or not (zero l CESTIA-CN1L Dipartimento di Elettronica e Informazione, Politecnico di Milano, via Ponzio 34/5, 1-20133 Milano, colorni@elet.polimi.iL laniado@elet.polimi.it 2 Poliedra, via Fucini 2, 1-20133 Milano, muratori@mailer.mip.polimi.it