In 2011 and 2015, the Texas Transportation Institute at Texas A&M released an “Urban Mobility Report” which grabbed a lot of headlines, like “Washington area tied with Chicago for traffic congestion, study finds.” The study led me and many others to write articles debunking its bad methodology.
Well, it’s four years later, and TTI has dusted off the study and updated it, apparently without really engaging with the criticisms the last two times around. Now we have WTOP saying “DC-area car commuters spend more than 100 hours a year in traffic, study finds,” and asserting that the Washington region’s traffic is the third-worst in the nation.
City Observatory writes,
After a four year hiatus, the Texas Transportation Institute has once again generated its misleading Urban Mobility Report—and it’s still wrong.
The UMR has been comprehensively debunked–it has never been peer-reviewed nor have its authors responded to authoritative critiques, it relies on a series of false premises, penalizes cities with compact development patterns and short commutes, ignores non-automobile travelers, and exaggerates all of its key claims.
City Observatory will have an updated debunking soon, but meanwhile, here’s a repost of what I write in 2011 and 2015. We’re reposting it with some edits and updates. I’ve given the report a quick look and the critique here seems to still apply, but I haven’t scrutinized the entire report.
What’s wrong with “Washington’s traffic is third worst in the nation”?
The report’s predecessors and, it seems, the current iteration look at only one factor: Whether traffic is moving fast or slow at a given time. Consider two hypothetical cities. In Denseopolis, people live within two miles of work on average, but the roads are fairly clogged and drivers can only go about 20 miles per hour. However, it only takes an average of six minutes to get to work despite always being “in traffic,” which isn’t bad.
On the other hand, in Sprawlville, people live about 30 miles from work on average, but there are lots and lots of fast-moving freeways, so people can drive 60 mph. That means it takes 30 minutes to get to work, almost none of which is “in traffic.”
Which city has worse roads? By TTI’s methods, it’s Denseopolis. But it’s the people of Sprawlville who spend more time commuting, and thus have less time to be with their families and for recreation.
For example, in the 2011 report, TTI ranked Portland as worse than Nashville, with a Travel Time Index (TTI) of 1.15 for Nashville and 1.23 for Portland. However, because of greater sprawl, Nashville commuters spent an average of 268 hours that year commuting, while the average Portland commuter spent 193 hours. It’s just that Nashville commuters weren’t in traffic as much.
Does this mean build more roads?
What does this mean for public policy and the Washington region? TTI’s data is often used to justify spending money on new freeway capacity, since congestion sounds bad. Tim Lomax, a co-author of all three reports, told the Post’s Ashley Halsey III in 2011, “You can do little things like stagger work hours, fix traffic-light timing and clear wrecks faster, but in the end, there’s a need for more capacity.”
“That we are congested is not news, but TTI’s report does tremendous damage, because they fail to recognize the primary cause of our congestion and imply that we could simply widen roads to build our way out of the problem,” said Stewart Schwartz of the Coalition for Smarter Growth, about the 2011 report.
Since 2011, statements from TTI have been slightly less roads-only in their focus, but Lomax told AP this time, “I think it is pretty clear that everything isn’t happening enough,” referring to adding capacity to the transportation system. And the report’s focus on traffic congestion for car commuters means that solutions which help some people take a different mode wouldn’t give cities credit on the total number of hours drivers spend in traffic.
The real answer is to reduce dependence on long commutes
Technology can help people get around more easily, but there are bigger-picture policies as well to help people not have to drive so far in the first place. To do that, we need to concentrate future growth around existing hubs with more residents, jobs, and multimodal transportation.
That’s what the Metropolitan Washington Council of Governments (COG) has been trying to push since before the first TTI report with its Region Forward plan and the related 2010 “What Would It Take?” scenario (PDF). These involve focusing development in places like Tysons Corner and the Route 1 corridor in Fairfax, around underutilized Metro stations in Prince George’s, future ones in Loudoun, and MARC and VRE hubs in Maryland and Virginia.
Arlington achieved substantial job and resident growth in its Rosslyn-Ballston corridor without adding to traffic congestion, as has Montgomery with growth in Silver Spring and Bethesda and DC development in places like NoMA and the Capitol Riverfront area. Regional leaders should be less concerned with speeding up existing cars, which just leads to sprawl farther out, and invest more in finding ways to grow the region without adding traffic.
Washington has grown while managing congestion
In fact, that’s just what the Washington region has done. Between better location and transit, the original report showed congestion did not increase from 1999 to 2011 even on TTI’s scale. That means our region had been successfully growing without adding traffic. Instead of “Washington area tied with Chicago for traffic congestion, study finds,” which was the 2011 Post headline, it could have read, “Washington area’s traffic hasn’t gotten worse in a decade thanks to smart growth.”
In his article about the 2015 report, Halsey reported that “traffic delays in most parts of the country have bounced back to pre-recession levels.” But in Washington, the TTI report’s numbers hardly budged from 2012 to 2014, according to spreadsheets from the 2015 report. The Silver Line, which opened between the 2011 TTI report and the one in 2015, reduced traffic by 15% at some intersections while also offering many people new choices to get to work.
This time, the report focuses on total numbers of hours the median driver spends in traffic: in Washington, that’s 102 in 2017, the most recent year of data in the report. That number still appears to revolve around how much time is in “congested roads” versus “uncongested ones” as if free-flowing roads have zero negative consequence (as in Sprawlville).
Comparing years, the latest report says our region’s number rose to 102 from 99 hours in 2016, 96 in 2015, and 90 in 2012. It doesn’t say how much came from people moving to places with longer commutes or what the number is with travelers who use other modes.
The new report does seem to have a new approach in quantifying the number of hours spent in traffic rather than the percentage of time spent in traffic. A city which helps shorten people’s commutes from 30 minutes in traffic to 20 minutes in traffic, say, would indeed end up with a lower number of hours per year in traffic. But the focus remains on total “hours of delay” rather than the actual times people spend commuting, which is what really matters.
For more critiques of the TTI methodology, see City Observatory’s page. Meanwhile, I’ll set a reminder for 2023, when presumably it’ll come back again.