Traffic Congestion and Reliability: Linking Solutions to Problems
Mitigating congestion is a high priority for the Federal Highway Administration (FHWA), which has established congestion as a key focus area.8 The Traffic Congestion and Reliability: Linking Solutions to Problems Report supports this effort by providing a review of congestion in the United States. The emphasis of the Report is on measuring trends in travel time reliability and making travel more reliable through initiatives in Transportation System Management and Operations (TSM&O). The topic of congestion is clearly much broader than this focus. While the broader context of congestion is discussed, the Report spends most its effort on defining and measuring travel time reliability, and highlighting TSM&O strategies to address it. Among the important features of this report are:
- Focus on travel time reliability. The Report extends the total delay-based statistics in the Texas Transportation Institute's Urban Mobility Report9 with statistics on travel time reliability, a topic of increasing interest in the transportation community.
- Investigate the root causes (sources) of congestion. Understanding the causes of congestion leads to more effective strategies for dealing with it.
- Explore the impact of congestion on freight and the economy. Congestion not only affects individual travelers (primarily commuters) but also truck travel and costs as well as the economy as a whole.
- Present performance measurement as a process for making things better. How the transportation system performs is significant not just at the global level presented in the Report — it also can be used to make changes in day-to-day activities like traffic incident management and to develop more effective transportation investments.
- Highlight the effects that both operational improvements and physical capacity expansion can have on congestion. As we present later, operations versus capacity expansion is not an "either/or" proposition. Rather, these activities are complementary and each has an important role to play in alleviating congestion. This is especially true given that recent history has taught us that no single strategy can effectively address congestion — only through a combination of strategies can congestion be controlled.
- Identify how congestion affects everyday life in the U.S. The Report develops a series of "vignettes" showcasing the effects of congestion on the daily activities of the public.
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 in congestion measurement 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.
8 Federal Highway Administration, FY 2003 Performance and Accountability Report, http://www.fhwa.dot.gov/reports/2003performance/index.htm.