TTI Urban Mobility Report Bungles Congestion Analysis Yet Again

Check it out, congestion is getting better! Source: TTI

At the risk of repeating ourselves: The Texas A&M Transportation Institute (TTI) got it wrong again.

Their 2012 Urban Mobility Report (using 2011 data) just came out [PDF]. Like every year, they tout their “improved methodology,” but the authors still haven’t made the changes that would make their congestion rankings meaningful in the real world.

Not only that, they continually sound the alarm about how much worse congestion has gotten in the last 30 years, but they fail to note (except in the chart above) that we must be doing something right these past six years because congestion is down significantly from 2005. It probably has something to do with the fact that Americans are driving less.

TTI’s Travel Time Index measures congestion based on how much longer it takes to drive a road in congested conditions than free-flowing conditions. They’ve now upgraded to a Planning Time Index, which appears even less useful. The PTI is a measure of the extra time a traveler would need to allow for to arrive on time for “higher priority events, such as an airline departure, just-in-time shipments, medical appointments or especially important social commitments.”

Extra time to make important trips. Source: TTI

If the PTI for a particular trip is 3.00, a traveler would allow 60 minutes for a trip that typically takes 20 minutes when few cars are on the road. Allowing for a PTI of 3.00 would ensure on-time arrival 19 out of 20 times.

PTIs on freeways vary widely across the nation, from 1.31 (about nine extra minutes for a trip that takes 30 minutes in light traffic) in Pensacola, Florida, to 5.72 (almost three hours for that same half-hour trip) in Washington, D.C.

That number earned DC the nation’s worst congestion ranking this year.

I don’t know how realistic this PTI is — who really allows for nearly three hours to make a half-hour trip? But more important: If you had to budget three hours for a trip that would only take half an hour driving in good conditions, wouldn’t you start to look for other transportation options? However far that “half-hour” trip is (they don’t give mileage) you could probably bike it in less than three hours.

One useful change the report authors made this year was the inclusion of carbon emissions attributed to traffic congestion. They calculate congestion’s toll on the ozone layer at 56 billion pounds – about 380 pounds of carbon per car commuter. A total of 2.9 billion gallons of fuel is burned in these traffic jams.

Of course, that’s not the whole story. If they’re trying to get at unnecessary emissions and fuel use, they should include all the automobile trips that are made alone that could have taken on passengers; all the trips made by car that could have been done by transit, foot or bike; and all the trips made longer by the fact that poor street design and land use decisions have spread residences, amenities, and services so far apart that every trip requires a car. If they want to figure out the carbon emissions that are cooking our planet without reason, TTI would be well served to start with those.

And that’s the problem with TTI’s rankings, and it’s what we say every year: To rank cities’ congestion based on nothing but freeway speed misses the point and risks incentivizing terrible transportation decisions. The Washington, DC region has excellent transit options, so its citizens don’t have to sit in three hours of traffic. We have miles of useful bike lanes, on- and off-road, inside and outside the city limits. We even pioneered the use of slug lines, which allow car-free commuters to catch rides with strangers who want to use carpool lanes.

How long will it take you to reach your destination using those travel options? What if you move to a first-ring suburb or, god forbid, the city? TTI doesn’t say. It doesn’t rank cities based on the multiplicity of alternatives to sitting in mind-numbing, air-smogging traffic.

TTI does do lip service to the need for transportation options, recommending a “balanced and diversified approach to reduce congestion – one that focuses on more of everything.”

Some areas might be more amenable to construction solutions, other areas might use more travel options, productivity improvements, diversified land use patterns or redevelopment solutions,” they write.

And buried inside the report, with no mention in the press release, is their annual report on the benefits of public transportation – for drivers, that is. If your metro or bus commute saves you time, makes you happy, gives you time to read or sleep, and gets you to work on time – well, bully for you but that doesn’t figure in to TTI’s index. All they care about is how much it helps motorists for you to have your behind on a subway seat instead of the driver’s seat.

Last year, transit saved 56 billion vehicle-miles and 865 million hours of delay for drivers. That’s 450 million gallons of fuel and $20.7 billion. The great majority of that savings was in just 15 “very large” urban areas. Americans who are driving less, or not at all, sure are helping those who haven’t kicked the habit. 

TTI also measures the savings from “operational treatments” (though the report buries the definition in a footnote 50 pages after the first mention). The treatments include freeway incident management, freeway ramp metering, arterial street signal coordination, arterial street access management and high-occupancy vehicle lanes. These systems save drivers 374 million hours a year, and could save another 468 million hours if they existed on all roads.

7 thoughts on TTI Urban Mobility Report Bungles Congestion Analysis Yet Again

  1. Of course Tanya, we can use the findings to our advantage as well, can’t we?  When I go around the country, I point to TTI’s data and conclude (the following is right out of a paper that I sent to one of my clients):  “The failure of auto oriented transportation
    solutions has been documented by congestion data collected by the Texas
    Transportation Institute since 1982.  439
    Metropolitan areas have been studied; in spite of the massive investment in building
    high speed roadway capacity, congestion indicators are skyrocketing out of

    I definitely understand everyone’s frustration with how some will use the report, and have expressed to Tim Lomax of TTI directly my feelings about how they could do a better job of framing.    But until they balance the interpretation of the findings themselves (I suspect they won’t), then we should start to do it for them.  How is this for starters:

    Universally, during the 20th
    Century, transportation was viewed as an end in and of itself and state DOTs
    furiously pursued congestion relief by adding more capacity. And universally,
    it has not only failed to solve the problem, it has made it worse.   The failure of auto oriented transportation
    solutions has been documented by congestion data collected annually by the
    Texas Transportation Institute since 1982. 
    439 Metropolitan areas have been studied; in spite of the massive
    investment in building high speed roadway capacity, congestion indicators are
    skyrocketing out of control.It is time to tell the emperor that he/she is not wearing any clothes.

    The issue of how high speed automobile
    capacity affected land use development and spread out destinations and
    activities was considered as someone else’s business. The highly mobile
    transportation system (or “supply”) created spread out access, which in turn
    affected how people choose to locate their homes and businesses (land use
    patterns).  Conversely, spread out land use patterns further increased the
    demand for transportation (travel distances, modes, etc.), and this has become
    the eternal cycle that we now find ourselves in.  While originally
    accomplishing many positive outcomes, the single minded focus on high speed
    mobility has increasingly led to an ever growing series of unintended
    consequences, such as the undermining of all other modes of travel. In Cities
    around our country, streets have been tuned for high level of service for
    automobiles during the peak hour.  
    Virtually by problem definition, wide street designs stifle all other
    modes, inhibit livability and create barriers between places in urban
    areas.  To make matters worse, these high
    capacity designs often fail to deliver the desired Level of Service.”

  2. The NBC Nightly News report on this study was not as bad as it could’ve been, but they hardly mentioned transit and the blurb on bikes just showed some hipsters in Portland…not that there’s anything wrong with hipsters in Portland, but there are plenty of “normal” people out there riding to work every day.

    Also, they kept saying “commuters waste xxx amount of gas” or “commuters sit in traffic for xxx hours a year” I kept yelling “CAR commuters!”  Not all commuters are stuck in traffic congestion, but unfortunately it has become standard practice to use “commuter” as shorthand for “someone who drives to work”.

  3. @a489cfeb305eb04cd7295a9d0522e2af:disqus thank you for posting the CEOs for Cities link. Clearly I’m referencing Joe Cortright’s work on this; I should give him credit! @google-53ae50a2fd9d6f362f209c4fbe0c3659:disqus thanks for the eagle eye — I fixed the error. @yahoo-G3WNQXTTTU32SMXTV7ZQ6CAY7U:disqus saliva notwithstanding, DC has the second highest-ridership metro system in the country. What’s so funny about that? @bobafuct:disqus and @5bbaa03f5dfcef2029f5973f89347a45:disqus excellent points.

  4. “That number earned DC the nation’s worst congestion ranking this year.”
    It’s the “number of hours of delay per auto commuter” that earns DC top honors, and that has always been the focus of the TTI report.  

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