Measuring traffic congestion

A traffic congestion index was developed using data for California highways from 1976 through 1994. The technique yields a congestion measure that has several advantages. The index developed here can be applied to counties, urbanized areas, highway segments, or other portions of geographic areas or highway networks. The index allows cross-sectional and time-series comparisons that have only rarely been possible. What is most important is that the congestion index developed here is based on data that are readily available. The index is compared to others, based on Highway Performance Monitoring System data, and similarities and differences are illustrated. Important issues for future research and data collection efforts that can contribute to more refined congestion measurement are also discussed.