Policy Study

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

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, Tennessee needs just over 2,750 new lane-miles at a total cost of $5.0 billion, in today’s dollars. That’s a cost of approximately $51 per resident each year. Tennessee ranks 12th out 50 states and the District of Columbia in terms of most lane-miles needed and 17th in the total costs of those improvements. If the state made these improvements, it would save over 47 million hours per year that are now wasted in traffic jams.

Tennessee has two cities that currently suffer from severe congestion, which this study identifies as areas with Travel Time Indices (TTIs) of 1.18 or higher. The Memphis and Nashville-Davidson areas are the 35th and 49th most congested regions in the United States, with TTIs of 1.22 and 1.18, respectively. This means that driving times during peak traffic hours are 22 and 18 percent longer than during off-peak times.

Unless major steps are taken to relieve congestion, drivers in these parts of Tennessee can expect to see TTIs of 1.40 and 1.34 by 2030. For an idea of how severe these levels of congestion would be, projections for Memphis are equivalent to traffic delays in present-day Denver and San Diego, and those for Nashville-Davidson are equivalent to present-day Minneapolis-St. Paul and Boston. But Tennessee can significantly reduce these congestion problems by adding about 2,750 new lane-miles by 2030 at an estimated cost of $5.0 billion in today’s dollars.

This investment would save an estimated 47 million hours per year that are now lost sitting in traffic, at a yearly cost of $4.25 per delay-hour saved. The annual cost to relieve severe congestion in the Memphis and Nashville areas alone are significantly lower, at $1.93 and $2.85 per delay hour saved, respectively. 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 49 suggests, the other cities in Tennessee with populations of over 50,000 are currently less congested than Memphis and Nashville, with TTIs in the 1.04—1.05 range. However, the relative increase in delay projected over the next 25 years for these cities is between 75—280 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 1.09, cities like Clarksville and Johnson City are facing future traffic delays similar to those currently experienced in much larger cities like Buffalo, Pittsburgh, and Cleveland.

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» 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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