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Building More Roads Only Causes More Traffic

Expanding highways and roads increases congestion by creating more demand—and building more public transportation doesn't help the problem.

heavy traffic

A quick drive on one of Los Angeles's many freeways illustrates the fact that having more roads doesn't necessarily prevent traffic. Now a study from the University of Toronto confirms it: Expanding highways and roads increases congestion by creating more demand. And building out public transportation systems doesn't help either; there will always be more drivers to fill up any new road we build.

The disheartening study used data from hundreds of metro areas in the U.S. to reach the conclusion that there is a "fundamental law of highway congestion," which essentially says that people drive more when there are more roads to drive on—no matter how much traffic there is. As a result, increased building of "interstate highways and major urban roads is unlikely to relieve congestion of these roads."

Not even building more trains, buses, and light rail can help with the traffic problem. In an interview with Streetsblog, study coauthor Matthew Turner explains that his fundamental law means that people are always waiting for extra space on the roads, and a person taking the bus simply opens up space for a new car:

If somebody stays home, or if you add capacity to the road, there’s somebody there waiting to use that space. Well you should expect the same thing to happen if somebody gets out of their car and gets on the bus, it’s bringing up a little bit more room on the roads, and there’s somebody out there waiting to use it.

This doesn't mean public transportation is worthless; it transports more people with less fuel and fewer carbon emissions. But spending more on it has no effect on traffic.

So what does help? The University of Toronto researchers offer just one suggestion: congestion pricing. It's a pain for commuters, but that's sort of the point. People are desperate to drive, so if you want less traffic, you have to make it harder for them.

[Image: Wikipedia]

Reach Ariel Schwartz via Twitter or email.

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  • John Winslow

    The root of the problem is that the car has radically transformed the landscape. Like heated gas molecules, cars move at high speed and they exert a pressure that pushes apart the nodes of daily life - home, offices, shopping, schools, etc. And we are now stuck with a landscape that requires high-energy transportation to traverse. All we can do is price different modes - bus, car, train - in a way that encourages or discourages one over the other. In a saner world, we'd be able to walk or bike the required distances, without strain. In a saner world, nobody would conceive of 50-mile daily commutes, and the like. In a saner, more self-powered world, there wouldn't be one class of people who can afford to travel outside of crowded rush hours and another class stuck in traffic so much of the time and yet another class waiting for buses in the rain. If you want equity - and that's what we're told is the political goal of this society (No Child Left Behind, etc. etc.) - then you do away with energy consumption on the scale we now take for granted.

  • Dahlia

    The problem is urban planning. There is so much waste of space in accommodating parking lots, and landscaping decorations, it's impossible to walk from one block to another in places like LA and Houston. If you look at older colonial cities like Boston, you realize that they mix businesses and apartment buildings together (having floor shops and apartments above. The roads are narrow and there are little shops and restaurants lining up the streets thus making neighborhoods walkable and lessens the need for cars. 

    Other cities like Paris, Montreal, and Tokyo curb the need for cars by densifying neighborhoods instead of expanding them. So yes, adding roads and highways only encourages the need for cars. What LA needs to do is stop wasting space with their lawns and rethink spacing altogether. Penalizing drivers won't curb their need to drive, it'll only make them angrier on the road.

  • SCS

    This article reminds me of a quote from Ronald Reagan: Governments view of the economy is:  “If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.”  The most stunning conclusion in the study: “Our results strongly support the hypothesis that roads cause traffic.”  WOW! 
    Caution:  The study did not look at the effectiveness of charging drivers for each mile they drive, known as “congestion pricing” (taxing the moving) or conclude that it was an effective solution to the congestion problem. It only concluded that it was the only solution still on the table.
    The most cogent conclusions in the study:  1. "We find no evidence that the provision of public transportation affects VKT" (Vehicle Kilometers Traveled.) So why don't we stop subsidizing it to the tune of four dollars for every rider!  2. Cited studies found that access to an interstate highway in a rural county causes increases in the level of local economic activity, leading to large increases in retail earnings, an overall increase in firm earnings and population increases. More people means more traffic, more business means more commercial driving, trucking and migration. So why don't we stop subsidizing population “density” in big cities that already have too much traffic. Why don't we stop fighting “suburban sprawl” and send the new roads to the rural areas (read that JOBS) where most people really want to live anyway.

  • Garl Boyd Latham

    "Why don't we stop fighting 'suburban sprawl' and send the new roads to the [formerly] rural areas..."?

    Well, perhaps it's because some of us aren't ready to give up on the future!

    The cancer we've helped create may eventually kill us all, anyway - but just think how much faster our society will implode (coagulate?) if we throw up our hands and "stop fighting 'suburban sprawl'"!

    Garl B. Latham

  • WMD

    This is classic progressive liberal research! Invent an answer that pushes the progressive agenda forward (for example the need to control people). Do a study that will support the needed answers. Now, and this is key, have a liberal group like FastCompany feature this research between a few good articles. This gives progressives another tool to dumb people down, at the expense of tax payers! 
    Maybe this is how Global Warming was invented?

  • William Field

    I can't believe how bss aackward and flawed this thinking is. Lets break this down. Traffic congestion is a problem why? It inhibits people from getting to where they need to go on a timely basis. Proposed solution? Decrease road ways and charge money to use them! I know I am not the only person see that the only outcome of this is to further inhibit people from traveling. I would say that the majority of driving in the US is done to accomplish a necessary task. (getting to and from work, School, Groceries, Doctor, and so on.) Can you think of even one occasion that the addition of a roadway influenced your decision  to drive? I can think of occasions that the addition of a roadway has eased traffic. And what about extreme circumstances like the emergency evacuation of a large area?   I see congestion pricing as all cons and no pros          

  • Tom W

    They keep looking at the same two pieces of the equation, cars and roads. There are just too many people living too far from work. Live closer to work and use birth control.

  • Cordell Wise

    If what Mr. Turner is describing is true, congestion pricing won't work either.  He describes a condition of unlimited demand (or at least demand that it so high that it has outpaced roads' or public transit's ability to accomodate it into the forseeable future). If that's the case then with congestion pricing only people who can afford it (or those who can't afford not to - read commuters) will drive on the roads but they will be no less congested.  Congestion pricing is just a tax on commuters.  It's not like I choose to sit in traffic! And if I have to pay more I'll choose to not go to work anymore! 

  • Garl Boyd Latham

    "...if I have to pay more I'll choose to not go to work anymore!"

    Oh, come on!

  • Tony W

    While I've added the full study to my "to read" pile, I think the piece that is missing is does it help overall driving time? 

    While traffic is irritating, isn't it generally faster to take the interstate than navigate the street network? 

    Intuitively it seems the case, as wouldn't some of the regular commuters take alternative routes if it was not either more convenient or efficient?

    Tony W.

  • Norm Wright

    Widening a road to relieve congestion is like loosening your belt to lose weight. It only provides temporary relief. The only proven, effective road network that has less congestion and more safety is also our oldest one: the grid street network. Grid street networks with multiple paths always outperform highway-centric "arterials". And public trans is naturally a wonderful thing to also shift users to more efficient modes of travel but even buses get stuck in traffic. So the study shows congestion pricing as a solution but the greater solution, albeit more costly, involves not only congestion pricing but also a greater development of rich street networks that have a grid pattern. A hundred small roads providing multiple paths to your destination is always better than one large highway providing only one route.

  • Scott Byorum

    Really?  I guess they never studied the widening of Hwy 101 through Santa Rosa and Windsor.  Used to be grid lock in peak hours.  Now with an extra lane, everything is cleared up.  Maybe in populations that are growing signifigantly, this might be the case.  But drivers don't go out of their way to fill roads just because they are expanded.  Oh neat!  There's a new lane in LA and I live in SF.  I'm going to drive 800 miles down there to fill it up, just like everyone else I know!

  • Rodney Imai

    There may be some general truths to their study, but as a veteran of southland traffic, I remember how bad traffic was on the 5 Freeway near Disneyland, prior to Disney demanding that they widen the freeway before they built California Adventure compared to today where AM northbound traffic on the 5 Freeway (Orange County to LA) is wide open until you leave Orange County and the Freeway narrows by 2 lanes... it then becomes packed for the next 15 miles to Downtown LA.

    My experience has been that the most subtle changes to a freeway can mark the difference between 65MPH and 25MPH.  Dedicated lane for off ramp.  Short merge lane.  Mislabeled signage.

    A blanket statement that expanding freeways or public transportation only attract traffic seems false...rush hour traffic isn't a choice, people need to travel at that time.  If they could avoid it they will.... but look at what a holiday or even Friday morning traffic in LA is like comparatively.... there isn't an endless supply of commuters out there waiting to take up the slack that can be created by improved roads or public transportation.  I feel like we just haven't been bold enough to find out where that threshold.

  • Ray Wilson

    Taxing commuters seems counter productive.  The congestion is an artifact of providing means for greater demand.  The road is a productive resource.  Isn't that the purpose of building it?  Is we don't want people to use roads, change the demand influences that make roads a useful tool. Taxing is like breaking legs to slow down the rush to the exit when there is a fire.

  • John Vasko

    I will read the study itself but I find it hard to believe that building the RIGHT public transportation options would not help. I agree with congestion pricing.