This report describes an evaluation approach, process, and analytical tool set that were developed to analyze freeway usage and performance in the central Puget Sound region. It also functions as a user's guide, describing the range of performance measures used and the methods and tools available to estimate them, along with step-by-step instructions.
This report also serves the important purpose of documenting the analytical assumptions and limitations of the evaluation method. This report is one of three products of a Washington State Department of Transportation (WSDOT) project to enhance the department's ability to monitor and improve its traffic management efforts on Seattle-area highways, and to provide useful information to the public and decision makers about the status of the freeway system's operational performance. This report is primarily intended to meet the first of these objectives. In addition to this report, this project produced a set of software tools to assist in freeway data analysis, as well as a research report documenting the level of traveler usage and travel performance on the principal urban freeways in the central Puget Sound area for 1997. The freeways studied in this project are managed by WSDOT using its FLOW system, a coordinated network of traffic monitoring, measuring, information dissemination, and control devices that operates on urban state and Interstate highways in the central Puget Sound region.
The data analysis procedures described in this report are intended to facilitate a series of periodic evaluations of the central Puget Sound urban highway network and the WSDOT FLOW system. They were also designed to have general capabilities, so that they can be employed at any freeway location of interest, provided that the appropriate data have been collected. This evaluation process focuses on mainline (GP and HOV) performance measures; plans call for eventual expansion of the process to include other aspects of the WSDOT FLOW system.