USE OF TRAFFIC FORECASTING MODELS IN THE DEVELOPMENT OF TRAFFIC MANAGEMENT PLANS FOR CONSTRUCTION OF THE CENTRAL ARTERY/TUNNEL PROJECT

The Central Artery/Tunnel (CA/T) Project is a $6 billion federal highway project to be constructed in downtown Boston and adjacent areas. The major components are a Third Harbor Tunnel (I-90) linking downtown Boston and Logan Airport, and a new underground 8- to 10-lane Interstate highway (I-93) in downtown Boston to replace the existing 6-lane elevated highway. The construction will affect traffic operations in one of the densest urban environments in the United States. The purpose of this paper is to describe the transportation planning approach to manage traffic during this construction. The focus of this paper is on the extraordinary extent to which the CA/T project team is attempting to predict and mitigate the impacts of construction on traffic congestion and air quality. This effort has already resulted in major changes in construction staging and traffic management plans. The first section of the paper describes the CA/T Project and the accompanying traffic management issues that have been raised. The second section of the paper describes the process for developing traffic management plans, with particular attention on the interaction between traffic forecasting, traffic engineering, and the design of construction stages. The third section presents a case study of how the traffic forecasting process contributed to a change in the traffic management plan. The fourth section describes the application of traffic forecasting to air quality analysis, and the fifth section describes the approach to analyzing the role of public transportation as a traffic management mitigation measure.