Policy Study

Mobility Project – State-by-State Analysis of Future Congestion and Capacity Needs – Washington

How bad will traffic congestion be in 2030? How much construction and how many new lane miles will each state and major city need to add over the next 25 years to prevent severe congestion? And how much will it all cost? The Reason Foundation study Building Roads to Reduce Traffic Congestion in America’s Cities: How Much and at What Cost? and its addendum, A Detailed State-by-State Analysis of Future Congestion and Capacity Needs, provide in-depth answers to these questions. An interactive map ranking the states by congestion and costs to reduce traffic is here and a map of the most congested cities is here.


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To significantly reduce today’s severe congestion and prepare for growth expected by 2030, Washington needs just under 1,500 new lane-miles at a total cost of $6.9 billion, in today’s dollars. That’s a cost of approximately $58 per resident each year. Washington ranks 22nd out of 50 states and the District of Columbia in terms of most lane-miles needed and 15th in the total costs of those improvements. If the state made these improvements, it would save over 205 million hours per year that are now wasted in traffic jams.

Washington has one city that currently suffers from severe congestion, which this study identifies as areas with Travel Time Indices of 1.18 or higher. The Seattle-Tacoma area is tied with Detroit as the 12th most congested region in the United States, with a TTI of 1.38. This means that driving times during peak traffic hours are 38 percent longer than during off-peak times.

Unless major steps are taken to relieve congestion, drivers in this part of Washington can expect to see a TTI of 1.79 by 2030. For an idea of how severe that level of congestion would be, note that this projection is significantly worse than the traffic delays experienced today in places like Atlanta, Chicago, and San Francisco. Indeed, it is even higher than Los Angeles, the most congested area in the United States with a TTI of 1.75. But Washington can significantly reduce this congestion problem by adding about 1,500 new lane-miles by 2030 at an estimated cost of $6.9 billion in today’s dollars.

This investment would save an estimated 205 million hours per year that are now lost sitting in traffic, at a yearly cost of $1.34 per delay-hour saved. The annual cost to relieve severe congestion in the Seattle area alone is significantly lower, at $0.96 per delay hour saved. This does not account for the additional benefits not quantified in this study, including: lower fuel use, reduced accident rates and vehicle operating costs, lower shipping costs and truck travel time reductions, greater freight reliability, and a number of benefits associated with greater community accessibility, including an expanded labor pool for employers and new job choices for workers.

As Table 54 suggests, the other cities in Washington with populations over 50,000 are currently less congested than the Seattle area. However, the relative increase in delay projected over the next 25 years for these cities is 88—150 percent, which will be sharply felt by local commuters. (The ‘delay’ in the travel time is the portion of the TTI over 1.0.) With TTIs of 1.10, cities like Bremerton, Kennewick-Richland, and Olympia-Lacey are facing future traffic delays similar to those currently experienced in much larger cities like Buffalo, Pittsburgh, and Cleveland.

(click here for larger image)

» Return to Index Page: Study, State-By-State Data, Maps
» Return to Interactive Map of Traffic U.S. Congestion Statistics and Construction Needs

This information is excerpted from A Detailed State-by-State Analysis of Future Congestion and Capacity Needs and Building Roads to Reduce Traffic Congestion in America’s Cities: How Much and at What Cost?

Additional Resources:
» Reason Foundation’s Mobility Project Main Page
» Reason Foundation’s Transportation Research and Commentary
» Reason Foundation’s Press Room

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