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A lot rides on how USDOT defines "congestion"

Congress has done its job, such as it is, and passed a transportation bill. Now it's handed off the policymaking to USDOT, which must issue a raft of rules, definitions, and guidance to accompany the new law, known as MAP-21. According to sources with intimate knowledge of this process, much depends on how DOT decides to measure congestion.

Photo by Joe Shlabotnik on Flickr.

New performance measures for the Congestion Mitigation and Air Quality Improvement program (CMAQ)—and quite possibly for the entire national highway system (depending how they define "roadway performance")—require a working definition of congestion.

If the agency follows the prevailing orthodoxy, states could be rewarded for wasteful highway spending. If it adopts better measurements, smarter investments and less wasteful spending will follow.

The CMAQ measures will also require a definition of "cost-effectiveness," a related but somewhat separate can of worms.

Graphic from CEOs for Cities.

The above graphic shows the wrong way to measure travel performance. The "Travel Time Index" awards a better score to Charlotte than Chicago, even though commutes in Chicago are shorter, because drivers in Charlotte spend a higher percentage of their time in free-flowing traffic.

USDOT should include distance driven in any measure of congestion

Performance measures in the MAP-21 law have been criticized for being toothless, since many of them don't have consequences attached. However, there is still the possibility that state performance rankings could be made public. And a spotlight on state failures could be an effective way to encourage good decisions.

Streetsblog asked Joe Cortright for his advice to DOT officials struggling to define congestion. Cortright is an economist and senior policy advisor for CEOs for Cities. In 2010, the organization commissioned him to write Driven Apart, a critique of prevailing methods of measuring congestion. His words of wisdom for USDOT: "Don't make the mistake the Texas Transportation Institute makes."

TTI's Urban Mobility Report, released every year, invariably gives top honors to places that have overbuilt road capacity. The institute measures congestion only by looking at the degree to which traffic slows down people's commutes. The problem with that, Cortright says, is that "you end up rewarding places that encourage people to drive longer and longer distances, and then you look at those long distances that they're traveling, and say because they're moving at a relatively higher speed much of the time that they're driving, that the system is somehow performing better."

Over the past few years, USDOT has been very deliberately working hand-in-glove with HUD and the EPA to treat transportation and land use as one cohesive system. It only makes sense that the agency use the same ethic in measuring roadway performance and congestion. By doing so, DOT would have to acknowledge that a long commute along miles and miles of free-flowing highways is no bargain compared to a short commute in dense traffic, not to mention an even shorter commute on transit.

Clark Williams-Derry, research director for the sustainability-focused Sightline Institute, suggests that congestion may simply be the wrong thing to measure. "Focusing on congestion is like, in a basketball game, focusing only on the number of assists you get," Williams-Derry said. "It's an interesting fact, but it doesn't tell you the final score."

But people treat this one piece of the picture as if it's "the whole story," he says. Why not measure how long it takes to get from place to place? Or how much it costs? After all, a major argument against congestion—and the reason that congestion reduction is elevated to a national priority—is that time spent stuck in traffic is lost productivity, which adds up at a national level. But the TTI method actually masks how projects affect total travel time, and wouldn't help measure productivity gains or losses.

The upshot is that following the same methods as TTI's Urban Mobility Report to set performance goals under MAP-21 would be a huge mistake. "It would focus resources on projects that are sprawl-oriented, that encourage decentralized development," Cortright said. "You can raise your performance on that measure most by having people drive more, as long as they're driving faster."

Cortright recommends that DOT put more emphasis on vehicle miles traveled than travel speed, and notes that this is especially important when it comes to measuring the cost-effectiveness of projects that are supposed to mitigate congestion and improve air quality. That's another tricky definition DOT is going to have to figure out.

It's not cost-effective for USDOT to encourage projects that induce driving

When DOT decides how to judge the cost-effectiveness of a CMAQ project, they can either focus on the CM (Congestion Mitigation) or the AQ (Air Quality), but those aren't the same thing. "It's unambiguous that if people drive fewer miles there's going to be less pollution," Cortright said. "A lot of the quote-unquote 'congestion reduction' projects essentially encourage more VMT."

Widening roads induces more people to drive, which makes it a poor method to address congestion. Image from Todd Litman at the Victoria Transport Policy Institute.

"There's this pervasive mythology that our pollution problems are chiefly caused by people having to idle in traffic," he continued. "There's no evidence for that, and the evidence there is suggests that if you reduce congestion, people actually drive further, and that more than offsets the benefits of less idling."

In addition, Williams-Derry pointed out that not all congestion is stop-and-go traffic. Congestion that consists merely of slower but smoothly flowing traffic actually improves air quality, since cars work more efficiently at slower speeds. That's what makes CMAQ a tricky program to judge, since its two goals are sometimes at odds with each other.

If DOT is going to measure cost-effectiveness, Cortright and William-Derry say, it needs to think like a business. Starbucks would never build a second cafť next door so that it could move the line faster at 9:00 a.m. and then have it sit empty the rest of the day. Building more roadway capacity to handle peak-of-the-peak traffic makes just as little sense.

Cost-effectiveness also can't be measured without examining what are known as "externalities"—the costs of driving that are passed on to the public. "The existing gasoline tax doesn't even cover the maintenance on the highway system that we have now," Cortright said. "It doesn't reflect the economic losses to crashes, it doesn't reflect the economic externalities associated with the environmental effects of burning all this gasoline and putting carbon in the atmosphere, and it doesn't reflect the foreign policy and military costs of being so dependent on foreign oil."

"If I were USDOT, I'd try to add in, in figuring cost-effectiveness, the cost of all those other subsidies to automobiles," he added.

There are still people inside and outside DOT—including some of the authors of MAP-21 inside the halls of Congress—for whom the only cost-effective transportation solution is to expand roads so cars can move faster. Not only would this do nothing to solve the problem of congestion, it would actually exacerbate the air pollution that the CMAQ program is designed to address.

By being thoughtful about how to define success in the CMAQ program specifically, and roadway performance generally, USDOT can have a tremendous and lasting impact on whether our transportation system is sustainable and sensible—or whether it drives us off a cliff.

Tanya Snyder is the former editor of Streetsblog USA, which covers issues of national transportation policy. She previously covered Congress for Pacifica and public radio. She lives car-free in a transit-oriented and bike-friendly neighborhood of Washington, DC. 


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Thank you for pointing out that transportation doesn't exist in a vacuum and that it is intrinsically tied to our place-making and land-use decisions.

It's tough because DOT's job is transportation and it can be difficult to get those officials to realize that transportation is only a piece of a larger puzzle. Helping coming up with measures that take this into account is a good first step.

by drumz on Aug 16, 2012 1:08 pm • linkreport

I agree that the notion of measuring "congestion time" by itself is ludicrous. The measuring stick should be commuter-hours. If you want to be all green about it then measure total emissions. Of course none of this means squat if the proposed alternative is too expensive (gas, tolls, parking, and/or fares) so user cost should be measured too. What is less clear to me is how to balance the three. There you go, economists, have at it.

by movement on Aug 16, 2012 2:09 pm • linkreport

"Starbucks would never build a second café next door so that it could move the line faster at 9:00 a.m. and then have it sit empty the rest of the day."

>>>Sure they would. There are many instances of Starbucks opening multiple stores *very* close to each other to handle the high demand. Grocery stores install extra check-out lanes to create more capacity for higher demand periods. Many businesses plan their "capacity" for the peak "demand" period. So do transportation agencies.

"Building more roadway capacity to handle peak-of-the-peak traffic makes just as little sense"

>>>>Why? Support the argument. How should transportation agencies plan for demand? Metro plans for peak periods in the design of their stations for people movement, as well as the capacity of their ROW infrastructure (the rails). Metro is currently limited on the capacity of the Orange Line due to a constraint at the Potomac River tunnel. They have high demand during two periods of the day (AM and PM) on weekdays. Metro plans their service around peak periods. Why should this not be done for our raodways as well?

by Matt on Aug 17, 2012 1:40 pm • linkreport

"Starbucks would never build a second café next door so that it could move the line faster at 9:00 a.m. and then have it sit empty the rest of the day."

They most certainly have!

There are intersections in Manahattan where there's a Starbucks store at or near each of the four corners.

by ceefer66 on Aug 17, 2012 2:29 pm • linkreport

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