Decisions concerning activities" both in: ,the personal sphere and in industry and 'government, may be considered as being the result of a choosing process effected on a collection of possibilities (activities, projects, measures etc.). Any estimable consequences of the possibilities considered can also be included in the choosing process, so that necessary efforts and expected results can both play a role. On some occasions these consequences are objectively determined, measured and quantitatively known. On others, they are subjectively determined, estimated and only qualitatively appraised. There has been no lack, during the last few decades, of attempts to make the decision making process explicit or to develop decision-making models. There is extensive documentation concerning the application of such models in many specialized fields, including transport, traffic and traffic safety. In particular, considerable attention has been devoted to cost benefit analyses. This is in fact a book-keeping type of estimation in which the problems lie mainly in assigning financial values to phenomena which have no demonstrable value in terms of money, but can exert such an effect on welfare that they deserve high priority when policies are; being drawn up. This is particularly the case where life, health, possibilities of human development, joie de vivre, and comparable human values are at stake. It is no wonder that it is publications on cost/benefit analysis in the field of traffic safety in particular that give this problem such an emphasis. A decision making criterion that only considers the financial consequences of traffic accidents is difficult to accept, keeping in mind that it is this factor of human suffering caused by injuries and fatal accidents that, while difficult to quantify, gave so much priority to combating traffic hazards. The need for an effective decision making technique able to contribute to an optimal determination of priorities is still just as valid. Reactions in the documentation to methods of cost/benefit analysis vary from tense expectation to expressions such as "nonsense on stilts". In what follows, a decision making model will be put forward that has been developed for solving policy problems in such a way that in addition to the financial aspect, one or more welfare aspects will play a role. The contribution of a measure to general welfare is calculated as the weighted sum of the effects per component of welfare. The ratio of the increase of general welfare to the costs of bringing about the measure is used as a comparison factor. The cost/benefit model can be regarded as a special case in which all other than financial components are assigned a zero weighting. Three essentially different types of decision making problems can be distinguished: 1. Must a measure be brought into effect or not? 2. Which of two more available measures is preferable? 3. Which of a group of mutually compatible measures or projects should be given priority? The model has been developed for solving the third type of decision making problem, but can also be useful for the two other types.
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