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The Dream of a Tunnel Under Dallas

DigdugOn April 7, I posted an item about an op-ed written by Michael Morris of NCTCOG and Bill Hale of TxDOT. I questioned why the two men would predicate a teardown of I-345 on the construction of the Trinity Parkway when, in a 2007 memo, Morris didn’t include I-345 on a list of projects that depended on construction of the Parkway. A NCTCOG spokeswoman named Amanda Wilson emailed me Friday to clarify. The link between I-345 and the Parkway wasn’t made in 2007 because I-345 is a maintenance project, not a project to increase capacity. Morris and Hale have now linked I-345 with the Parkway because only now are people talking about reconfiguring I-345. Duly noted.

The spokeswoman also took issue with something I wrote in that post about the “inner loop” that Morris and Hale mentioned in their op-ed. They wrote:

“Consideration should also be given to a new ‘inner loop’ study that would address how to move traffic from I-35E to the Hospital District to Love Field, and on to the Dallas North Tollway, Central and I-30.”

I said that unless I was mistaken, Morris was talking about widening Mockingbird so that it could handle more traffic. The NCTCOG spokeswoman said that wasn’t true, and she asked me to go back and review a conversation I’d had with Morris when we met to talk roads a few weeks back. Wilson, the spokeswoman, wrote, “When you came out to our offices to talk to Michael, I know this ‘inner loop’ concept was part of that discussion and I would ask you to maybe go back and review that conversation, which was more about tunnel (not surface) improvements that could move traffic from IH 35E through the hospital district over to DNT, Love Field, and possibly even connecting over to IH 30.”

She is right. Morris did mention a tunnel to me. But that notion is so preposterous that when I saw mention of an “inner loop” in the op-ed, I speculated in my earlier post that any such loop would have to run along Mockingbird, for at least part of its length. Perhaps I should not have speculated. Perhaps an “inner loop” tunnel actually could be built built from I-35 to I-30.

They are trying to build such an inner-city tunnel in Seattle right now. They’re having a little trouble. But the 1.7 mile tunnel is supposed to cost about $3.1 billion. To my eye, an “inner loop” tunnel in Dallas from I-35 to Love Field to the Tollway would run 2.5 miles. Continue to Central, and you’ve got a total of 4.5 miles. All the way around to I-30 would put you in the ballpark of 7 miles. Depends on the route, course. Using Seattle as our guide, though, that would put the cost of Morris’ tunnel in Dallas at $12.7 billion.

As I say, perhaps this tunnel is possible. But there must have been a reason why Morris and Hale didn’t mention it in their op-ed.

  • AmyS

    Why not tunnel I-345 again?

  • Tim Rogers


  • Greg Brown

    Is that the same lack of money to build light rail and upgrade the surrounding roads that will take up the traffic if I-345 is removed? Oh, that’s right, the traffic will just magically disappear. If one can believe in that magic, then a 7-mile tunnel sounds quite sane.

  • Wylie H Dallas

    What the heck?!?!? Has Morris completely lost his mind?

  • Margaret Hunt Hill

    It’s about $1.4B. Doable if we tear out I-345 and decide later that we need new capacity there,

  • WalkableDFW

    One definition of magic is that which can not yet be understood, in this case by our existing traffic models, which like many of our current economic models externalize that which they can’t understand or properly measure thus giving them huge blind spots. Two of these are related to context and the density of an area. The traffic models don’t take into account density and densities ability to reduce 1) trip length and 2) total amount of trips. Instead, the traffic models think McKinney Texas produces the same amount of travel demand as McKinney Avenue. They simply take the amount of built space and extrapolate out a number of trips. According to the model, the densest areas need the biggest roads because they don’t adequately account for alternate forms of travel.

    Related to this is two recent studies. Arizona DOT found that dense areas result in a 30% reduction in average trip length. A 30% reduction in trip length is the equivalent of adding 30% in new capacity without adding any capacity because the same car isn’t counted over and over again. This is not adequately accounted for in traffic models.

    Also, San Diego is pursuing policy that must factor total trip reductions based on dense walkable centers. Apartment surveys in DFW have shown that walkable suburban neighborhoods (like Legacy) show a reduction of about 20% of total trips. In walkable urban areas such as uptown Dallas, there is a reduction of 40% of total trips. The trips are still happening. Economic activity is still occurring, so where did the trips go? They’re happening on foot, bike, or transit. Things we don’t measure. Therefore, walkable areas add capacity without actually adding any capacity.

    So yes, the traffic does magically take care of itself if magic in this sense is like fire to a caveman, which is the level of sophistication of our traffic planning, modeling, design, and understanding.

  • WalkableDFW

    No more than anyone whose mindset is stuck in the 1960’s. Dallas has just finally moved forward enough insofar as his thinking now looks rightly antiquated.

  • Greg Brown

    In summary, “We don’t know and we don’t know how to know.”

  • mdunlap1

    Because that isn’t necessary. A nice boulevard will do just fine. As with every great city in the world, people can either go around or spend a few extra minutes to enjoy the boulevard.

  • mdunlap1

    In summary, this has been market-tested elsewhere, the same fears were voiced in every case, and in every case they have failed to come true.

  • Ed P

    I know you know this, Patrick, but, brevity.

  • Dubious Brother

    Boston’s tunnel is nick named “The Big D” so we couldn’t use that but it is 3.5 miles long and was originally projected to cost $2.8 billion but will ultimately cost over $22 billion including interest. Those involved with the project should be out or getting out of prison soon so they would be available to consult.
    It hasn’t worked out too well for the global warming projections so I suggest that we borrow the hockey stick graph to represent the starting projections with the ultimate cost of tunneling from anywhere to anywhere.

  • Greg Brown

    So you are essentially paraphrasing Yogi Berra: It will be so crowded downtown with traffic that no one will drive there.

    The funny thing is, I would like to see this happen, but not without extra light rail, street improvements, and upgrading of our 80’s-era traffic light control system. To do otherwise is folly.

  • Johnyalamo

    There is no way Greenway Parks and HP would ever allow a tunnel from Love Field to the Tollway and Central. It’d be easier and cheaper to dig under NW Highway if you figure in a the lawsuit legal fees.

    Apparently Rio, in an attempt to be a so called world class city, demolished an overpass today for something called “The Olympics.” How the heck are those people going to drive to the Olympics when they are tearing down the freeway?

  • Greg Brown

    And don’t forget tearing down shanty towns, ultimately displacing tens of thousands. I guess, much like the traffic, they will just “disappear.” Talk about urban planning with the barrel of a gun.

  • Anonymous

    There’s nothing new about this. A private group — with credibility and funding — proposed a Mockingbird tunnel in 2000. Estimated cost then was $800M. Of course it was shot down by the Highland Park residents, even though they wouldn’t have even known it was there except for the reduced traffic.

    Some info at Great Laura Miller quote in there. :-)

    By the way, the Dallas area is generally considered to have near ideal conditions for tunneling. The rock’s soft enough for easy boring, but strong enough that you don’t need a lot of additional structural support.

  • Anonymous

    “Why not tunnel I-345 again?”

    You’ve got the DART subway under the north end. You’ve got I-30 below grade at the south end. You’ve got Interstate highway design requirements that limit the maximum grade (to 6% I believe). Basically, you’d have to rip out the subway at I-30 to tunnel I-345, and then where would you put them?

  • Anonymous

    If you can’t dazzle them with your brilliance, baffle them with your bullsh*t.

  • 1st anon

    In today’s all-about-me world, most people are going to be asking: “how does this affect ME?”. Are there any maps, studies, or animations that might show … “if I live here, and I want to get there, what would Google Maps tell me to do without I-345”

    From my perspective, the first thing that I thought was: “how cool, but omg, that’s going to be a PITA to get to Houston”. Then I realized how selfish, ’cause I only drive to Houston 2-3 times a year.

  • Ken Duble

    This is not a new idea. The idea of a self-funding toll tunnel under Mockingbird came up about 15 years ago, and HP residents thwarted it.