Transportation

How Traffic Studies Perpetuate a Traffic Congestion Obsession

The Texas Transportation Institute's new Urban Mobility Report peddles the myth that urban traffic congestion is a problem that can be solved

A few weeks ago, Texas A&M’s Texas Transportation Institute released its annual Urban Mobility Report. Every year since 1987, TTI has compiled what it refers to as the “definitive measure of traffic congestion in America,” a document that is intended to help inform transportation decision-makers and elected officials throughout the country on how to plan transportation improvements.

The release of the report, which is co-sponsored by the Texas Department of Transportation and the National Institute for Congestion Reduction, is usually covered by media outlets around the country. This year, the headlines reported that traffic congestion dropped in half in 2020 due to the pandemic, but it was steadily rising back. In other words, sorry folks, congestion isn’t going anywhere.

Solving this looming congestion problem, the report argues, is going to require a variety of solutions. But in reviewing the list of proposals in the report, they all tend to hover around a critical core assumption: reducing traffic congestion means coming up with ways to speed-up cars. That’s not a surprising conclusion. Over the past 30-plus years, studies and analyses of this type have tended to view reducing traffic congestion as the No. 1 transportation challenge facing urban regions.

But over on Planetizin, Todd Litman, the founder and executive director of the Victoria Transport Policy Institute, argues that this is one of a number of misleading assumptions baked into the Urban Mobility Report.

Litman’s analysis of the Urban Mobility Report targets a critical issue around transportation planning that has come up in many of Dallas’ recent transit debates, from the (now dead) Trinity River toll road to the proposed removal of I-345. Often, the perception of transportation needs is shaped by the narrow lens through which reports analyze transportation problems. Litman identifies some of these biases in the Urban Mobility Report. For example, the report only represents motorists’ interests; it doesn’t recognize that motorists are not only stuck in traffic, but they themselves are the traffic; and it only looks at the value of alternative transportation modes, such as public transit, as it relates to reducing traffic congestion.

Litman also argues that the report also lacks pretty basic academic rigor:

The UMR ignores basic research principles. It contains no literature review, fails to explain many assumptions or cite sources, does not discuss criticisms or potential biases, has no sensitivity analysis, and lacks independent peer review. It fails to give readers the information they need to understand its results.

What the report does give readers is a handy, clickable way to look at how their local communities’ traffic congestion ranks compared with the rest of the country. The appeal of this kind of list is understandable. We all experience traffic congestion in the same way – sitting in our cars and staring at the clog of cars in front of us, imagining that everything could magically speed up. The Urban Mobility Report attempts to put some hard numbers to this familiar subjective experience.

But this isn’t a good way to look at transportation – or even congestion. Litman points out that the report only evaluates automobile traffic conditions and contains no information about other forms of urban mobility, even though in many cities between 20 and 40 percent of trips during peak commuting times are made by walking, bicycling, and public transit.

This ends up skewing the report’s results. It ranks cities like Boston, New York, and Washington D.C. as among the most congested cities, but this is true only when you ignore the fact that many people in these cities don’t have to rely on their cars to commute. The report also doesn’t take other transportation planning goals into consideration in its analysis, such as affordability, safety, and social equity. Transportation mobility is boiled down to congestion and congestion only. And congestion, the report reminds us, is expensive, costing Americans some $101 billion in 2020.

But even this congestion cost calculation is skewed, Litman argues. It exaggerates the cost of congestion by using higher travel time cost values than recommended by many transportation experts. It exaggerates the fuel savings and emissions reductions achieved by reducing congestion. And it ignores the fact that expanded roads have residual costs for both commuters and communities, including incentivizing increased vehicle traffic, increasing neighborhood pollution, and dividing and devaluing urban areas.

These biases overestimate congestion costs, exaggerate roadway expansion benefits, and undervalue other congestion-reduction strategies. The newest UMR estimates that congestion costs averaged $605 per motorist in 2020, but that should be viewed as a higher bound estimate; more realistic baseline speeds, travel time costs, and fuel consumption models reduce this to $150-300 per motorist, making it a modest cost overall. Most motorists seem to agree, although they complain about congestion, few support decongestion pricing or major tax increases that would solve this problem.

Unsurprisingly, a report that sees congestion as the prime problem facing urban transportation tends to recommend road expansions as a prime means of relieving this costly symptom. The Urban Mobility Report does warn elected officials against believing that any one solution can solve cities’ transportation problems, but it goes on to recommend a range of potential solutions that all revolve around auto-centric approaches. These include things like focusing on roadway management, improving traffic signals, removing car wrecks more quickly, and offering improved trip planning technology.

Oddly, the report found that congestion levels dropped considerably in 2020 as more people switched to working remotely, and yet it doesn’t suggest that increasing these hybrid working schedules could achieve long-term traffic reduction. And it of course suggests adding roadway capacity, but then it warns readers that large urban areas are always going to congested to some extent. As Litman points out, it’s a curious paradox – to admit that roads won’t ultimately eliminate traffic congestion but telling elected officials to build them anyway.

Road expansion is a cure-all, but it doesn’t consider that new roads and roads expansion generate additional vehicle traffic. It also doesn’t weigh other benefits of non-auto approaches to reducing vehicle congestion, such as the way multi-modal transportation options help promote affordability, safety, equity, and environmental benefits.

In Texas we’re used to this kind of myopic thinking. The logic and assumptions baked into the Urban Mobility Report represent the transportation orthodoxy that has helped create the world we live in today – sprawling metro areas whose success only increases the costs of transportation. Growth has only created more crowded roads requiring more public dollars to chase an endless cycle of highway expansion. The report attempts to export Texas’ simplified narrative around transportation:

Its biases are significant because planning decisions often involve trade-offs between different solutions. For example, road space can either be used for general traffic lanes or bus lanes, and money spent to expand roads is unavailable for other purposes. By exaggerating congestion costs relative to other impacts and ignoring generated traffic impacts, the UMR tends to overvalue urban roadway expansions and undervalue other congestion reduction strategies that provide more co-benefits, such as the congestion reduction strategy that also increases affordability, improves public health and safety, or reduces pollution emissions.

Is there a better way to analyze transportation needs? Litman believes so, and he outlines several improvements in his piece. These include, but are not limited to, looking at overall transportation system accessibility – how easy it is to get between two destinations – rather than simple travel speed. More accurate transportation studies should also focus on the individual traveler, and not only motorists, so that pedestrian and cycling efficiency and delays (sometimes caused by auto-centric infrastructure) can be incorporated into the results. There should also be consideration of the costs motorists impose, rather than simply looking the costs motorists bear.

“Congestion tends to maintain a self-limited equilibrium,” Litman says. “It increases to the point that delays limit further peak-period vehicle travel.”

In other words, the problem with looking at urban mobility purely through the lens of vehicle congestion is that it ignores a basic conundrum: we will always be able to add cars to roads faster than we can build roads to accommodate them. Congestion isn’t a problem to be solved; it is an essential characteristic of urban highways.

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