The Traffic Congestion and Reliability: Linking Solutions to Problems Report provides a snapshot of congestion in the United States by summarizing recent trends in congestion, highlighting the role of unreliable travel times in the effects of congestion, and describing efforts to curb congestion. In particular, the Report develops a framework for understanding the various sources of congestion, the ways to address congestion by targeting these sources, and performance measures for monitoring trends in congestion. Much of the Report is devoted to measuring recent trends in congestion. One of the key principles that the Federal Highway Administration (FHWA) has promoted is that the metrics used to track congestion should be based on the travel time experienced by users of the highway system. While the transportation profession has used many other types of metrics to measure congestion (such as “level of service”), travel time is a more direct measure of how congestion affects users. Travel time is understood by a wide variety of audiences – both technical and nontechnical – as a way to describe the performance of the highway system. All of the congestion metrics used in the Report are based on this concept. The different aspects of congestion are discussed using a variety of data sources, with perhaps the newest aspect being the role of reliability in the congestion problem. The variation in travel times is now understood as a separate component of public and business sector frustration with congestion problems. Average travel times have increased and the Report discusses ways to reduce them. But the day-to-day variations in travel conditions pose their own challenges and the problem requires a different set of solution strategies. (Author/publisher)
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