The Counterintuitive Impacts of Traffic Congestion and Road Widening

By Dom Nozzi

The conventional wisdom claims that widening a road will reduce traffic congestion and fuel consumption.

The conventional wisdom is wrong.

Newman and Kenworthy are the scholars to read on this issue. Their studies persuasively show that the reverse of the conventional wisdom is true.

Research has found that cross-culturally and throughout history, humans, on average, will live in a place that creates a round-trip commute time of approximately 1.1 hours per day. Therefore, when we widen roads, the faster commute time that is briefly created will enable more dispersed residential sprawl to get us back to the 1.1 hour equilibrium.

People, in other words, drive longer distances (and drive more often) when a road is widened. In a growing community, that means the congestion is not reduced. And the increased driving increases the amount of fuel consumed.

This sprawling, dispersing impact of road widening is inevitable, regardless of how aggressive your land use plan is in controlling sprawl.

In many locations within the US, we have seen an upward trend in the number of roads that are now highly congested. This has happened despite the fact that this country has spent trillions of public dollars over the past several decades to try to reduce congestion by widening roads. Given the growth in congestion traffic jam on huge hwy (and the failure to reduce congestion in the long run) despite all the widenings, this strategy has failed catastrophically. It is perhaps the most costly, misguided and damaging action taken in human history.

Indeed, the trillions we have spent to widening roads has actually created new car trips that would not have occurred without the widening — thereby validating both the studies of Newman & Kenworthy, as well as the “Triple Convergence” described by Anthony Downs. The Triple Convergence states that when a road is widened, three things inevitably occur. First, motorists who had been taking alternative routes to avoid the congestion now converge back on the widened road. Second, motorists who were avoiding congested times of day now converge back on such rush hours. And third, motorists who had opted to use transit, walk or bicycle to work start converging back to driving by car after the road widening.

In a growing number of American communities, the response to congestion is to let it be. This approach is known as “planned congestion,” and is the preferred strategy for such communities because of the enormous costs of widening roads, the benefits of congestion, and the counterproductive consequences of widening. I am an enthusiastic supporter of planned congestion for several reasons. Fighting against congestion by widening a road is part of the road-building, home-building and auto-maker lobby paradigm, because they know that if we try to fight congestion, we will get more road widenings, more cars, more car travel and more sprawl.

One of the many benefits of congestion is that, as transportation planner Ian Lockwood says, congestion creates a “time tax” for motorists. That is, the motorist pays a “fee” when they are slowed down. That “fee” is the time they lose in congestion. Conversely, then, the “time tax” created by congestion contracts our residential patterns as people seek to maintain that 1.1 hour equilibrium I mentioned above.

In our political climate, it is nearly impossible to use much more efficient and effective tactics: that is, to have motorists pay the real cost of their travel through high gas taxes or congestion (toll) fees. Instead, we keep motorists on welfare by not having them pay directly for the roads they drive on, or the time of day when they drive. All of us pay directly for water and electricity and food based on how much water, electricity and food we consume. Why not take the same approach with driving?

Because it is so politically difficult to directly charge motorists on welfare for their driving, the easiest way to control excessive driving (particularly at rush hour) is to indirectly charge the motorist by letting congestion happen. By not widening the road. By not adding turn lanes. By not timing traffic signals.

As Walter Kulash says, fighting congestion by widening a road is like loosening your belt to fight obesity.



Visit my urban design website read more about what I have to say on those topics. You can also schedule me to give a speech in your community about transportation and congestion, land use development and sprawl, and improving quality of life.


Or email me at: dom[AT]

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Filed under Energy, Politics, Sprawl, Suburbia, Urban Design

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