Stephen Rees's blog

Thoughts about the relationships between transport and the urban area it serves

Study: Building Roads to Cure Congestion Is an Exercise in Futility

with 3 comments


In a paper to be published soon in the American Economic Review, two University of Toronto professors have added to the body of evidence showing that highway and road expansion increases traffic by increasing demand. On the flip side, they show that transit expansion doesn’t help cure congestion either.

It seems that the professors have done another meta study. That means none of this “most comprehensive dataset  ever assembled” is actually new – it simply gathers together all the data they can find from as many studies as possible. The findings are not new either. In fact they concede that too, their work simply confirming the “fundamental law of highway congestion” suggested by Anthony Downs (1962; 1992). Or the equally extensive study by MVA/ESRC in 1998  “Traffic Impact of Highway Capacity Reductions” (1998) which showed that the obverse was also true. That when you lose highway capacity the congestion does not get any worse either. People adjust their driving. Indeed I have lost count of the number of times I have repeated the mantra: traffic expands and contracts to fill the space available.

They go on to point out that building new transit capacity of itself does not cure congestion either. And that is because if the new transit takes some auto trips off the road then  those drivers are replaced by others. Indeed the only measure that reduces congestion is road pricing. That does not mean we should not build transit. It is also worth repeating in this context that the Vancouver experience – detailed in yesterday’s posting and quoting Peter Judd, is that automobile demand can be reduced by sensible land use policies that enable more people to choose to walk to work than our current low density sprawl everywhere outside of downtown Vancouver. The mode split on Central Broadway (the second largest concentration of jobs in the region) being not that much different to the rest of the region.

The case for transit should not based on a false assumption – that it cures congestion – because it is clear that it has not. That does not mean that congestion is inevitable – but it has mainly so far been left to regulate itself. The outcome that produces is an equilibrium which produces a general level of equal dissatisfaction – the compromise that dissatisfies everyone equally. We all complain about congestion but we continue to add ourselves to the traffic flow when it suits our own purposes. That is because congestion is an externality: the cost is borne by everyone, not just those who make the decision to add themselves to the traffic flow.

Since the study is all about transportation – and transportation is a derived demand – the lack of discussion about land use in the Streetsblog article is disappointing but not unexpected. The City of Vancouver made a decision not to add to road capacity. Copenhagen went an important step further, it decided to steadily reduce the capacity not just of the roads in terms of vehicle movements but also of parking. It indeed has been argued – by Gordon Price (and no doubt others aware of the obvious) that the City simply could not afford to buy enough land to widen any of its arterials. He based his calculations on the cost adding short lengths of turn lanes to some Knight Street intersections and then extrapolating that to the length of the current system.

Many advocates of road building have gone on to assert that more road capacity is necessary to accommodate growth. This can be challenged on several levels. Firstly, is growth actually desirable? And if you do not accommodate it with new road, what then happens?  Most places that are growing get roads automatically – the developers pay for them. In most places developments are not permitted to proceed until  the traffic studies are done and commitments made to accommodate more vehicle trips: a self-fulfilling prophecy. What the road advocates ignore is that there are plenty of examples where there was no room for more roads yet there was still growth. Both Vancouver and New York demonstrate that. And in both cities the inefficiency of relying on single occupant vehicles for personal mobility is well understood. There are more people – and jobs – in both places, but they get around without (on the whole) being accompanied by tons of personal machinery. They walk, ride bicycles and use transit. There are taxis, rental cars, and other mobility solutions like car co-ops, but those are not for every day trips. Indeed, even the people who drive all the time will usually admit they do not actually need their own car for every commute – but worry about what would happen if they might need it. Providing decent alternatives to allay that fear is a small but important part of policy making that seems to be largely neglected. Vancouver, for instance, has had a well documented taxi shortage for years. The condition persists simply because of the political power wielded by the very small number of people who own taxi licenses.

Indeed the only puzzle that I think is worth considering is why, given the weight of the evidence that has been available for years, we persist in making decisions that defy reality. The same process is clearly at work with man-made climate change. And largely due to the actions of the same people. Yet we continue to be locked into denial and debate, when the path we are taking is clearly disastrous. And those who point out the error are castigated. Again, a relatively small number of people with a very clear agenda tied to their own wealth seem to have dominated both debates and in BC seem to be winning much of the time. The carbon tax – and its futility – being only the most recent case.

It is also worth repeating that we need to consider what kind of place we want to live in. Again, we need to examine the sort of place which people move towards when given a choice. The fact that house prices increase as accessibility increases should give us a clue – especially if we  express some belief in the wisdom of markets. Vancouver has some of the highest priced real estate in the world. So the deterrence effect of our supposedly intolerable traffic cannot be that bad, can it? Any more than it has made apartments on Central Park West in Manhattan cheaper.  The suburbs had to be sold, and sold aggressively. Just as cars were to people who, up until then had been managing quite well without the need to own their own horse and buggy. And, as was pointed out many times, the suburbs were not the happy paradises their developers had promised. And commuting was – and still is – regarded as a huge waste of time. Yet we still find ourselves engaged in debates about density. Even though the arithmetic of population growth on a finite planet – or within a region constrained by mountains and sea – is unarguable.

Written by Stephen Rees

June 1, 2011 at 8:41 am

3 Responses

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  1. Maybe we need to get these guys into the same room as the Mayor of Coquitlam. He has 10 lanes for freeway parallel to 6 lanes of Lougheed, and still figures 4 lanes of United Boulveard a few mtres over will solve all his traffic problems:

    Pat Johnstone

    June 1, 2011 at 11:04 pm

  2. What I take away from this is that we should not be “afraid” to take away space from the cars. I will return to the previous post to argue that unless we take away space from the cars, then all the single family residential; and all the street-fronting apartments on double loaded corridors built on Vancouver arterials will continue their compromised existence.

    Residential fronting arterials in Vancouver (the conditions vary elsewhere in the Lower Mainland) face a cluster of threats:

    1. The space has been shown to be unsupportive for social functioning at the neighbourhood level.

    2. Residents facing Broadway report wiping their furniture with a white cloth, and turning it over to see it black. The implications of this level of soot pollution for the human lungs can’t be good.

    3. Noise pollution.

    4. Threat of life from traffic.

    The good news is that we can take away cars (here we are saying: without penalty) and put in surface transportation that returns many times more trips per day.

    It would help the argument if we could state how many trips per day.


    June 3, 2011 at 8:10 am

  3. Well presented. I’m beginning to realise one problem here is that there’s a government department with a specific mandate to build roads, which I can’t help feeling makes them rather keen to find new road projects to keep themselves in work.

    They know this theory, in fact the evidence suggests they use it to get what they want in the long term: they build a new ‘local bypass’ which just happens to connect to an autobahn, and then when traffic increases, they go to the next town and offer to build a ney bypass there as well, or a bridge, or a wider road… you get the idea. Then the next town is clogged up, and it goes on. If a town rejects the plan they’ll just wait a bit and come back with another equally destructive idea later: after all, there’s plenty of potential schemes at once, and redesigning keeps their planners in wirk and the budget ‘needs’ high…

    They were recently skulking about the village suggesting that whet we needed was a highly expensive new bypass to be bored under the village to link with a major road in the valley. In fact it was a link in a chain of roads to make a bypass around Stuttgart, but everyone was so excited they didn’t think to check the background to carefully.

    Fortunately it died again due to lack of funds, but they’ll be back if we manage to go back to ‘normal’ growth…

    Andy in Germany

    June 4, 2011 at 3:28 am

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