Evaluation Of Methods For Freeway Operational Analysis

The ability to estimate accurately the operational performance of roadway segments has become increasingly critical as we move from a period of new construction into one of operations, maintenance, and, in some cases, reconstruction. In addition to maintaining flow on our existing roadways, we are faced daily with issues of allocating funds to maintenance activities that will ensure the roadways continue to serve the needs into the future. This includes identifying needs for expansion, additional freeway interchanges, and changes in operational strategies, including HOV lanes or other lane restrictions designed to facilitate efficient traffic flow. Limitations on available funding make up-front analysis of alternative improvement strategies even more important. Traditional methods of analysis such as those provided in the Highway Capacity Manual were not designed to address many of the issues that are commonly faced today. In response, traffic engineering professionals have begun to employ more advanced tools for operational analysis. These tools often involve simulation models that provide very detailed measures of performance based on detailed user input. Based on the experiences of the Virginia Department of Transportation with respect to simulation models and the results of studies documented in the literature, basic guidelines are presented for the use of simulation analysis for freeways in Virginia. Several models we found to provide reasonable results in particular situations. It is, therefore, critical to identify the characteristics of the network to be analyzed and select the best tool based on these characteristics.