Promoting Bicycling, Walking or Transit Will Not Reduce Congestion


By Dom Nozzi

April 3, 2010

In my opinion, it is a tactical mistake for those promoting “active (generally non-motorized) transportation” to seek to demonstrate (or otherwise argue) that promoting bicycling, walking, or transit will result in congestion reduction, as my book (The Car is the Enemy of the City) points out.

First, cars consume an enormous amount of space (a person in a car consumes 17 times more space than a person in a chair). That means that only a tiny handful of motorists are needed to congest a street. Which means that nearly all cities worth their salt have a “congestion problem.” And those cities which don’t have such a problem are showing a sign of being sick or otherwise dying, or at least losing attractiveness.

It has been shown over and over again by researchers such as Anthony Downs and Todd Litman that (in any city that is not in decline) we see space freed up when motorists become non-motorists. This freed up space is almost immediately taken by newly-recruited motorists who had previously been diverted by the congestion (via induced demand, or as Downs would say, the “triple convergence”).

And when the congestion fails to decline despite lots of time and money spent on non-car travel, the pro-car/pro-sprawl advocates quickly point out that these non-car efforts are a naïve waste of time and money. And that we should get serious and opt for the default solution: road widening.

Given all of the above, it seems to me that the progressive tactic is not to claim that promotion of non-car travel will REDUCE congestion. No, I believe it is much better, tactically, to point out that we need to establish ALTERNATIVES for those who wish to escape the congestion: rail trails, connected streets, compact and higher-density housing near jobs, HOT lanes, flex-time work schedules, etc.

The Car is the Enemy of the City also describes the many benefits of congestion for cities (benefits that are undercut when we fight to reduce congestion via the traditional tactics of widenings or signal timing, etc.). But I’ll not get into that now.

…Induced traffic and the triple convergence informs us that many travelers opt not to travel certain routes, opt not to travel at rush hour, or opt not to drive a car IF a route is congested. If the route is less congested (widening or mode shift, for example), those discouraged travelers “converge” back on the route, on rush hour and on car travel. The road congests again. And rather quickly. Unless the community is losing population.

Another way of putting this is that in our world, there will pretty much always be a latent demand for more driving. Much of that demand is discouraged or diverted by congestion. Much of the discouragement goes away when the road is less congested. Roads are not like pipes carrying water. They are more like pipes carrying gas. Expand the pipe and the gas expands to fill the larger pipe. We cannot loosen our belts to traffic congestionavoid obesity. We cannot widen our way (or shift modes) out of congestion.

As to the question of reducing emissions (a commonly cited benefit of reducing congestion), Jeff Kenworthy and Peter Newman convincingly showed about 20 years ago that congestion REDUCES emissions and gas consumption, despite what we’ve always believed (one of the great many benefits of urban congestion). Why? Because as implied above, congestion imposes what Ian Lockwood calls a “time tax.” And “low-value” car trips (driving across town to rent a video at rush hour on a major arterial, for example) decline.

Again, the key is not to REDUCE congestion. Congestion is a sign of city vitality. A healthy city cannot (nor should it) reduce congestion. A healthy city must provide ALTERNATIVES to congestion: convenient bicycling, walking, and transit, compact development, pricing roads and parking, etc. And all of these healthy alternatives are much more likely, politically, when there is a lot of congestion. It is no coincidence that those cities with the worst congestion have the best transit.

Congestion, in cities, is our friend. When we make it our “enemy,” we unintentionally join forces with the sprawl/road/car lobby, since the default solution for reducing congestion (the only one that works in the short run) is road widening.

One reason that congestion in cities is our friend is that, as Michael Ronkin notes, the most essential and effective way to reduce excessive car dependence (and promote walking/bicycling/transit) is to inconvenience cars. The most feasible way to inconvenience cars is to “let it be” when it comes to congestion. To NOT bankrupt ourselves and destroy our communities by widening roads/parking lots to reduce traffic/parking congestion.

Increasing the number of trips made by bicycling, walking, or transit not only will not reduce congestion. Such claims that increasing bicycling, walking, or transit will reduce congestion also perpetuates the downwardly spiraling, counterproductive EFFORTS to try to reduce congestion.

Those seeking a better community must end their (unintended) alliance with the sprawl lobby. Doing that means letting go of efforts to promote “congestion reduction.” And embracing efforts to provide ways to avoid the (inevitable) congestion.




1 Comment

Filed under Transportation, Urban Design

One response to “Promoting Bicycling, Walking or Transit Will Not Reduce Congestion

  1. Reblogged this on small town urbanism and commented:
    Traffic congestion is typically the number one complaint about Sebastopol. Being at the crossroads of 2 state highways and given the physical limitations of any expansion to the road network we have to live with what we have. The only way we are going to reduce congestion is to develop in a manner that people are able to reduce their automobile dependence. This reblog of a blog post from Dom’s Plan B blog is a good summary of why congestion is not necessarily a bad thing, and why efforts to improve congestion often do not have the desired outcome.

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