Opinion: More Roads Mean More Congestion

Last week the Texas Transportation Institute released an update of its Urban Mobility Report, which always gets a lot of attention because of how it claims to quantify the cost of congestion and how much time commuters waste sitting in traffic every year.

Predictably, this leads to calls for more roads and wider highways to “relieve congestion.” But this is 100% the wrong conclusion – and TTI’s own data proves it.

First, we should point out that the TTI congestion report has many expert critics who point out some critical flaws in its methodology and general framing around congestion. You can read a quick explainer here, as well as more detailed critiques here and here.

But let’s concede that people are driving more and congestion is bad. Does this mean, as AAA Maryland implies, that the solution is to build more roads and widen highways?

No, that won’t work and has never worked. And you can actually see this in TTI’s own data or rather, you used to see it in their data until they stopped including it in the report.

Here’s how: Let’s go back to the 2012 Urban Mobility Report and look at the spreadsheet of the data they used for the report. (It doesn’t seem to be on TTI website anymore, but we downloaded it back when it was released. We’ve posted it online here.)

In the spreadsheet, TTI reports a number of data points from 1982 through 2011, including population, vehicle miles traveled, hours of delay, etc. They still report most of these throughout all the updates they have done.

However, there is one thing that they don’t report any more: number of roadway lane miles. Why would they stop reporting that?

Maybe because it undermines the case for widening highways.

For example, in the Baltimore region, between 1982 and 2011 the region nearly doubled the amount of freeway lane miles (from 885 lane miles to 1,561 lane miles). During that same time, the region’s population grew from 1.7 million to 2.5 million – a 48% increase.

Freeway expansion far outpaced population growth, but it did not relieve traffic congestion. In fact, by every measure congestion got worse. The amount of congested lane miles increased from 31% to 58%. The annual hours of delay per auto commuter quadrupled, from nine hours a year to 41 hours a year. And the annual cost of congestion increased from $96 million per year to $1.5 billion per year.

Brian O’Malley

Growth in highway lane miles significantly outpaced population growth and yet, congestion got worse, not better. Why? Because more lane miles, and the accompanying auto-dependent suburban and exurban development that results, just meant people were forced to drive more. What other options did they have? In Baltimore, we haven’t built any new high quality, rapid transit since the Light Rail opened in 1992!

Eric Norton

And this pattern happens in metro regions across the country. For decades, study after study has found that expanding road capacity encourages more people to drive which, in as little as three to five years, soaks up that added capacity.

The most recent study to come to this conclusion was released just this year and found that a 1 percent increase in lane-miles induced a 1 percent increase in vehicle-miles traveled (VMT) – a one for one correlation. Moreover, after just five years the short-term increases in speed are wiped out and congestion returns to pre-project levels.

The evidence of this “induced demand” is so overwhelming that it is sometimes called the “Fundamental Law of Road Congestion.” A policy brief from the National Center for Sustainable Transportation titled “Increasing Highway Capacity Unlikely to Relieve Traffic Congestion” summarizes findings from over a dozen research papers found:

  • The quality of evidence linking highway capacity to increased VMT is high;
  • Increased capacity induces additional VMT in the short run and even more in the long run; and
  • Capacity expansion leads to a net increase in VMT, not simply a shifting from one road to another.

Increasingly, transportation professionals and departments of transportation around the country are recognizing this and responding accordingly. For example, the Colorado Department of Transportation (CDOT) has admitted that “simply accommodating more cars won’t work.” Shoshana Lew, head of CDOT said, “We are not going to be able to build our way out of congestion on a corridor where 85 percent of a growing population lives. The math just doesn’t work.”

The truth is there is no magic bullet to fix congestion. But there are ways we can lessen our dependence on cars and reduce the amount of time we spend in them. Mixed-use, in-fill development that brings jobs and residents closer together. Fast, frequent, and reliable transit service that connects to job centers. High-quality, separated bike facilities that make biking a true mobility option for everyone, not just those willing to risk their bodies riding with vehicular traffic.

No one wants to spend more time in traffic. We all want to spend less time on the roads and more time with our families, friends, and neighbors. But widening highways won’t give us that time. And that’s the real kicker with promising to fix congestion with wider roads; in reality, it condemns us to spend more time in our cars, not less.


The writers are, respectively, director of policy and programs and president and CEO of the Central Maryland Transportation Alliance.


  1. The essence of car travel is that the individual vehicles – not being coordinated but being driven by separate humans – need way more space than it first appears. If you consider a train, you can double the people by doubling the cars. If you add another track and double the cars, you move twice as many people with no slowdown. But with cars, when it gets crowded, there is inherent slowdown as each vehicle reacts independently. Jamming is intrinsic.ch

  2. Yawn. Same old tired misinformation. So the conclusion is supposed to be that there are real alternatives in the near term to facilitating mobility and sustaining the economy, but zero facts presented to support the inference. In reality when we restrict development and infrastructure, then the cost of housing close to jobs rises to levels where the average employee is forced to reside farther away and thereby endure long life sucking costly commutes.

    A second dynamic hiding behind this commentary is the Baltimore vs. Montgomery County wrestling match that has been going on ever since Montgomery County became a bigger economic driver than Baltimore City and the harbor. Central Maryland Transportation Alliance bristles at the prospect of the DC burbs implementing a large highway infrastructure project. Let’s see the record of where CMTA fought against the I695/I 95 interchange and I95 Express lanes on the city’s north side. Behind CMTA’s stated position here is the fact that they simply want more for the Baltimore MPO and less for the Washington Metro MPO. They are resentful that the Purple Line moved forward when the Red Line didn’t (a whole other story), Montgomery County has almost 1.1 million residents and contributes something on the order of a quarter of the tax revenue for the state, so some tilting of the infrastructure spending scales is going to exist.

    In the end, the build-no-roads position based on the fantasy that an adequate number of people can have their mobility needs served by mass transit, walking and biking simply can’t be supported with any data. Multi-modal is the only realistic approach. And even though mode shifts do indeed need to be progressively factored in over the long term, it is irresponsible to suggest that large scale shifts can be accomplished in anything short of multi-generational timelines. President Bill Cinton’s often quoted “It’s the economy stupid” statement still applies. If Maryland ignores the health of our economy in deference to economically stifling and prematurely forced transportation strategies, then we will have a lot more to worry about than induced demand arguments,

  3. If what you all are saying it is true, then they should be no traffic in the Washington Metropolitan Area. Maryland has the longest commuter time than any other state in the United States and funding more transit options instead of fixing our roads will further exacerbate the problem instead of fixing the problem

  4. Is this a question of which came first: The chiiken or the egg? The interstate highway system caused a lot of disruption, The driving reason it was built was for national defense: The ability to move military material across the country quickly. However, no one forecast the enormousositive impact the Interstate system would have on the American economy. And that’s what is at play here.
    As long as we have an influx of people, they will need housing. And with restrictiuons on growth, the only place housing can be found in the exurbs. And the only way you can get there is via roads.
    Transportation is a problem which can only be alleviated, not resolved.

  5. Mr Bethesda has his history wrong.
    Eisenhower pushed for the development of the interstate highway system after spending WW2 in Europe. He recognized that moving goods more efficiently would create an economic advantage. Fact is, our cost of transportation as a percentage of GDP historically hovered around 10% versus the rest of the worlds economies which cost 14-18%. Our highway system allowed us to be a lower cost producer of just about everything we manufactured.
    The road system also allowed Americans to travel more freely…..with their cars.
    I do agree that Transportation in general will always be a challenge given the need for new and unique solutions involving an “All The Above” approach. It’s unfortunate that Central Md Transportation Alliance wants to continues to advocate parochialism rather than seeing the bigger picture.

  6. Hi ETInOlney,

    Very sorry to bore you with facts. Your comments here include a number of spurious and inaccurate claims which I will address. But first we should be clear that nothing in your comment refutes the central point of the piece: building more roads (even beyond the rate of population growth) has not “fixed” congestion and, according to TTI’s own data, adding more lane miles has just made congestion worse.

    You say that “when we restrict development and infrastructure, then the cost of housing close to jobs rises to levels where the average employee is forced to reside farther away and thereby endure long life sucking costly commutes.” I think we’re in agreement on that, but you stating that in response implies that we support such restrictions. Nowhere in the piece do we call for restrictions on development and infrastructure. In fact, we specifically call for more infill development to bring jobs and people closer together.

    You say that we “bristle” at the proposal to widen these highways simply because they are located in the DC region and we want more money for the Baltimore region. You attempt to back up this assertion by asking about our record in opposing certain highway projects in the Baltimore region. The insinuation here is that we did not oppose those projects because it was transportation spending in the Baltimore region and that’s all we care about. In fact, we did oppose the I-95 ETL extensions and submitted formal comments in opposition which are a matter of public record.

    You say we are “resentful” that the Purple Line moved forward while the Red Line was canceled and imply it is this feeling that motivates our opposition to the proposed widening project. While we are obviously upset over the cancellation of the Red Line, we are not resentful of the DC region. We supported both the Red Line and the Purple Line and worked closely with DC area advocates to advance both projects. And, more recently, we publicly and actively supported the DC region in its efforts to secure dedicated funding for WMATA.

    You assert that due to Montgomery County’s population and tax contribution that there is “some tilting of the infrastructure investment scales”. Sure, Montgomery County is a large jurisdiction and contributes a lot to state transportation coffers, but Greater Baltimore holds 45% of the state’s entire population and contributes 49% of the state’s GDP. Additionally, according to estimates from the Department of Legislative Services the Baltimore region provides about 44% of the revenue to the Transportation Trust Fund. The DC region (Frederick, Montgomery, Prince George’s, and Charles counties) contributes about 34% to the trust fund.

    You say that “multi-modal is the only realistic approach.” We agree. What other approaches could there be? We see different modes as simply tools and technologies to help people have access to life’s opportunity. The problem is that for decades we have been over-reliant one tool, the car, to the detriment of all other modes. The system we have now is totally unbalanced and “multi-modal” in only the barest sense. We need to shift investments away from highway expansions and into bike/walk/transit and better land use to get to a healthier, more sustainable balance that is truly multi-modal.

    You close by saying that the strategies we propose (more transit, dense infill development, bike infrastructure) would be economically stifling. In fact, metro areas (like DC!) that have lots of dense, walkable urban places designed around and for people are more economically successful than car-friendly suburban places. We should be focusing our efforts on how to create more of these economically vibrant places that bring people and jobs closer together rather than just accommodating more cars.

    Finally, apologies if this is incorrect, but I’m guessing that ETInOlney is Emmet Tydings of the Suburban Maryland Transportation Alliance and founder of Citizens4Traffic Relief. If so, it would probably be in the public interest to disclose that here and not use a screen name.

  7. The logic of NIMBYer’s is almost laughable except that they have so much power in how the rest of us must suffer in traffic.
    The logic that more roads means more congestion is so illogical that my cat come up with a better excuse.

    If more roads meant more congestion, then according to that logic fewer roads would mean more congestion. By that logic if we reduced 270 to 1 lane than there would be no traffic. Certainly one can see how illogical that thought it.

    It’s equivalent to saying “we can’t bring more jobs here because that’ll just mean gridlock”.

    Point is, cars are here to stay for a long time. Whether the authors and NIMBYers like it or not. Their is no amount of rail, no amount of bus and certainly no amount of bicycles that will take enough cars off the road to make a difference. Period. So get real and build more, better and car friendly roads.


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