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Abstract
A framework is devised in which data obtained from a formal environmental impact assessment (EIA) of competing alternatives for a proposed civil engineering project is structured in order to aid the decision making process regarding the best option or group of options.
On the basis of a detailed examination, the ELECTRE III model is shown to be the most suitable methodology for choosing between complex civil engineering projects on the basis of predominantly environmental criteria. This model requires two basic sets of inputs for each of the criteria used as a basis for the decision: (a) A set of weights reflecting the relative importance of each criterion under consideration, and (b) A set of indifference (q), preference (p) and veto (v) thresholds for each criterion which allows the uncertainty associated with it to be expressed directly within the decision model.
Two new techniques have been developed by the author for the evaluation of both sets of inputs. For the importance weightings, Personal Construct Theory forms a basis for explaining how decision makers automatically place decision criteria into a hierarchy of relative importance. The new method is questionnaire based, with a pairwise voting system used to gauge the relative importance of criteria.
For the threshold values, a new, more comprehensive approach than has previously existed is developed for specifying realistic limits for p, q and v, within the context of an environmental appraisal. Both criterion error / uncertainty and human sensitivity to differing levels of the criterion are taken into account. Values are obtained for both quantitative and qualitative criteria.
The applicability of the new techniques is demonstrated with a case study which selects the best route for a section of proposed motorway going through the centre of Dublin, taking account of its environmental impact.