Abstract This paper presents an application of a Geographic Information System (GIS) in a traffic relief study. Traffic congestion has severely affected the environmental quality and the quality of life for residents in the study area. A team which consisted of planners, environmental specialists, historians, landscape architects, traffic engineers, and GIS professionals was organized to solve the problem. The environmental and socio-economic impacts of highway alignments have been evaluated from the very first step and every major decision-making for the duration of the project. The GIS professionals have played a crucial role in maintaining constant and active interactions among members of the project team, federal and state agencies, and the public. GIS has been used to develop natural and cultural resource inventory, to identify contamination sources, to assess environmental constraints and to evaluate proposed highway alignment alternatives. GIS provides an ideal atmosphere for professionals to analyze data, to apply models and to make best decisions. The high quality map products created with GIS enhance the quality of public presentations and reports. The authors feel that more people have realized the benefit of using GIS along with the progress of the project.