Driven Apart: How Sprawl Is Lengthening Our Commutes and Why Misleading Mobility Measures Are Making Things Worse

Something you probably already suspected: Nashville area traffic, including Murfreesboro and Rutherford County, is the most congested in the country.

A new report says Nashville area drivers spend 164 hours in peak time traffic, and purports that 120 of those hours, first in the nation, are a result of urban sprawl.

A new report from CEOs for Cities unveils the real reason Americans spend so much time in traffic and offers a dramatic critique of the 25 year old industry standard created by the Texas Transportation Institute’s Urban Mobility Report (UMR) - often used to justify billions of dollars in expenditures to build new roads and highways. The surprising analysis by Joseph Cortright, senior policy advisor for CEOs for Cities, says the solution to this problem has much more to do with how we build our cities than how we build our roads.

The report, titled Driven Apart: How sprawl is lengthening our commutes and why misleading mobility measures are making things worse and supported by the Rockefeller Foundation takes a new look at what’s really causing traffic congestion in America. The conclusions are far different than those of the UMR, which has long been used to measure traffic congestion.

“This analysis, once again, shows that many of the assumptions driving big investments of taxpayer dollars that shape our communities are outdated, said CEOs for Cities President and CEO Carol Coletta. Driven Apart adds to the growing body of evidence that shows compact development that puts many destinations close at hand has unexpected benefits — in this case, less time spent in traffic requiring less spending on highways. If we heed its findings, we’ll save time and money.”

Driven Apart ranks how long residents in the nation’s largest 51 metropolitan areas spend in peak hour traffic, and in some cases the rankings are almost the opposite of those listed in the 2009 Urban Mobility Report.

For instance, the UMR depicts Chicago as having some of the worst travel delays, when it actually has the shortest time spent in peak hour traffic of any major US metro area. In contrast, Nashville jumped from 31st to first on the list of those with the longest peak travel times.

While peak hour travel times average 200 hours a year in large metropolitan areas, Driven Apart proves that some cities have managed to achieve shorter travel times and actually reduce the peak hour travel times. The key is that some metropolitan areas such as Chicago, Portland and Sacramento have land use patterns and transportation systems that enable their residents to take shorter trips and minimize the burden of peak hour travel. If every one of the top 50 metros followed suit with Chicago and other higher performing cities, their residents would drive about 40 billion fewer miles per year and use two billion fewer gallons of fuel, for a cost savings of $31 billion annually.

“It is more critical than ever that the US’s transportation investments be guided by accurate data – especially during these difficult financial times, said Rockefeller Foundation Associate Director Benjamin de la Peña. Transportation costs are often the second highest expense for working Americans, and we must make sure we are providing more transportation options to help them stretch their budgets. The Rockefeller Foundation is proud to support Driven Apart as part of our initiative to promote more equitable and sustainable transportation.”

A close examination shows that the UMR has a number of major flaws that misstate and exaggerate the effects of congestion, particularly the Travel Time Index (TTI). TTI is the ratio of average peak hour travel times to average free flow travel times. Furthermore, for the 51 metropolitan areas analyzed in Driven Apart, the UMR overstates the cost of congestion by about $49 billion. Because this methodology does not take into account travel distances, it universally rewards cities that are spread out as opposed to compact urban areas.

"When it comes to understanding the nature of our urban transportation problems and how best to solve them, the UMR generates more heat than light, said Cortright. The Travel Time Index is a poor guide to making investments, and its time for a new perspective that highlights how we can make progress in reducing travel times through a variety of means."

Contrary to the UMR findings, Driven Apart says that many metropolitan areas have actually seen reductions in average peak hour travel times because residents are now traveling shorter distances, reflecting land use patterns and personal choices about where to live and work.

Rather than simply raising alarm about frustrating traffic delays, Driven Apart suggests new metrics that focus on trip distances and total travel times—two statistics not reported in the UMR— because they point to a broader and more powerful set of public policy options for dealing with urban transportation problems. The report recommends a new system for measuring urban transportation performance that includes emphasizing accessibility and focusing on measures of land uses, trip lengths and mode choices as well as travel speeds.

“The key role of sprawling development patterns in driving peak period traffic and the limitations of the Urban Mobility Report underscore the need for a much improved system for measuring and comparing the performance of urban transportation systems. Such a system should incorporate better and more precise data about speeds but also specifically track travel distances and land use patterns,” said Cortright.

“As someone who has long believed in the impact of land uses and community design on travel behavior, I am pleased to see this thoughtful critique of our inadequate approach to measuring traffic congestion. This report should be required reading for anyone interested in reducing the time Americans spend stuck in traffic and improving the livability of our communities,” said Congressman Earl Blumenauer.