Prioritizing traffic-calming projects using the analytic hierarchy process

The analytic hierarchy process (AHP), a multiple-criteria decisionmaking tool, is used to prioritize traffic-calming projects. AHP is proposed as an alternative to existing point scoring systems. Prioritization methods used in traffic-calming programs in Portland, Oregon, and Canberra, Australia, are applied; the results are compared to those of AHP. The three methods apparently produce similar rankings when applied to local streets that have speeding problems. AHP produces rankings different from those of the other two methods, however, when complex issues and qualitative factors must be taken into account. AHP may be more suitable in cases in which some factors cannot be quantified. In the examples studied, these factors included traffic diversion, the importance of the street, the impacts of existing traffic-control devices and measures adjacent to elementary schools, terrain, and neighborhood residents' opinions. None of these factors could readily be assigned a value in a point scoring system. Some of the concerns in applying AHP are the tediousness of making pairwise comparisons between alternatives, the consistency of the comparisons, and the defensibility of the scores. The decision maker should examine the scores to ensure that they are sensible and should be adequately aware of the issues so as to defend the scores. If there are n alternatives, then n(n - 1)/2 pairwise comparisons are needed. Clearly, for expedient application of AHP, the alternatives must be limited to a reasonable number.