Criteria-Based Decision Support System for Selecting Highway Alignments

Abstract

At the planning stages of a highway development process a number of candidate highway alignments are explored. While computerized highway optimization models can seek optimized horizontal and vertical alignments by minimizing aspects of total highway cost, selection of the final alignments is often influenced by environmental impact assessment and public and political participation. In order to ensure that there are no adverse impacts on the environment and the living conditions of the residential community, the Federal Highway Administration has initiated a context-sensitive design approach to highway design. A criteria-based decision support system is developed in this research for selecting highway alignments using genetic algorithms and geographic information systems, which can assist in estimating trade-offs among alignment-sensitive cost, alignment circuity, floodplain and wetland impacts, and intersections with existing highways. A procedure for selecting notably different alignments is proposed by evaluating alignments obtained at intermediate search generations by genetic algorithms. A set of different alignments can provide enough leeway to explore trade-offs among cost and environmental and roadway impacts. An example using Maryland’s geographic database is presented.