MAMCA-SIS (Multi-Actor Multi-Criteria Analysis Stakeholder-based Impact Scoring) is a novel appraisal method to support decision making in complex projects by quantifying the benefits and burdens of project alternatives for different stakeholders. It is distinctive from other quantitative evaluation methods in two fundamental aspects: 1) non-compensability, i.e. the distinction of positive and negative impacts; and 2) non-relativity, i.e. the scores accorded to the alternatives do not depend on the score of the other alternatives but only on a universal baseline.

The technique was developed for decision problems that cannot be addressed with the ranking algorithms of conventional MCA methods. All appraisal methods rely on two types of inputs: ‘objective’ facts (e.g. CO2 emissions, air quality), and the value or ideology-based valuation of these facts (e.g. the ‘value’ accorded to travel-time gains or human lives in infrastructure improvements). The strength of MAMCA-SIS lies in acknowledging the distinction between the objective and subjective components of the appraisal, and to use a factual base for the stakeholder-based valuations of impacts.