Recent statistics indicate a dramatic increase in congestion delay due to recurrent freeway bottlenecks. Proper identification of freeway bottlenecks and their causes is the key to formulating plans for reducing congestion. Relatively low-cost geometric and operational improvements can often mitigate the effects of a bottleneck. The paper presents the findings to-date on an ongoing NCHRP project on low cost improvements for recurring freeway bottlenecks. The research surveyed the state of the art and practice both in the US and overseas, proposed a definition of bottlenecks, bottleneck classification and mitigation measures, and developed a framework for analysis of freeway bottlenecks that can be applied using both real-time and historical data. A bottleneck identification algorithm was also implemented in an archival system of surveillance data. The end product of this research will be a technical guide with step-by-step application analysis of the bottleneck impacts, both local and system-wide, and determination and assessment of mitigation measures.
Abstract