How It Works: Fighting road congestion

How do you make traffic better? Curiously, not by simply building more roads

When the highways are clogged with traffic, what’s the answer? Logically, you’d think you’d build more roads to handle all the extra cars. As it turns out, that’s the worst thing you can do.

According to experts, adding new lanes actually makes traffic congestion worse. And on top of that, many road designs ostensibly intended to improve safety actually make them more dangerous for drivers and pedestrians.

When roads are widened, each new lane or mile of roadway congestion is matched 40 per cent with new trips almost immediately, according to Jeff Speck, city planner and author of the book Walkable City. Within four years, it’s matched 100 per cent by new trips. Basically, if you build it, they will come. Speck points to California’s massive 405 freeway expansion, which cost US$1.6 billion.

“It actually opened to congestion that was worse, and stayed worse, than it had been before construction,” he says. A traffic study concluded that afternoon speeds on the highway are the same or slightly slower than before the expansion, while along one busy stretch, the commute time is a minute longer. Meanwhile, adding lanes to the massive Katy Freeway near Houston, Texas, resulted in morning commutes that were 30 per cent longer than before, and evening commutes that ran 55 per cent longer.

The same thing happens when Canadian municipalities expand their highways. Speck says it comes down to induced demand, when an increased supply results in increased consumption.

“These are the people who were staying home, carpooling or taking transit because they didn’t want to fight congestion,” he says. When new lanes open and congestion initially drops, drivers who had switched to off-peak hours go back to their regular hours, while those who took transit get back into their cars.

So what happens when highways are reduced? When planners wanted to tear down San Francisco’s double-decker elevated Embarcadero Freeway in the 1980s — as many would like to do with Toronto’s Gardiner Expressway — opponents warned that neighbouring streets would be gridlocked. The California highway collapsed in an earthquake in 1989 and was not rebuilt. Congestion increased slightly but then fell, and the freeway’s footprint became a boulevard where, according to Speck, streetcars now transport more people than the highway did.

Incentives like improved transit help get people out of their cars, but there’s a risk that once they’re off the roads, other drivers get in theirs and pick up the slack. Instead, deterrents can be far more effective at reducing gridlock. In London, England, a controversial “congestion charge” began in 2003 and continues today, charging motorists to drive in the downtown core. The initiative resulted in a 30 per cent drop in congestion and a 20 per cent increase in cycling, and with bus service improvements when the revenue was funnelled into transit.

The Toronto highway tolls proposed by Mayor John Tory but rejected by the province could have worked to reduce congestion, provided they were high enough, Speck says. Drivers don’t pay the full cost of roads and infrastructure, which Speck says could be as high as $10 of public support for every $1 drivers spend.

“If you start to make driving begin to cost drivers as much as it costs society, through tolls or any other means, you begin to see more rational behaviour,” he says.

Congestion is only one problem cities face; another is poor road design. While most traffic lanes used to be no more than 3 metres (10 feet) wide, new roads are generally laid out with 3.6-metre (12-foot) lanes. In some cities, one-way streets can be three or four lanes wide, while two-way can be as wide as six or more lanes. Traffic engineers also set back fences and trees from the road, so that drivers who lose control don’t smash into them.

The result is a clear, wide path that resembles a highway, which in turn encourages motorists to drive faster. When the road feels smaller, they slow down and pay more attention. A Toronto study found that trees and other vertical objects close to the road edge resulted in a 5 to 20 per cent decline in the number of mid-block crashes. The size of city blocks also plays a role. Doubling the length of a block corresponds to a tripling of pedestrian fatalities.

Speck cites Vancouver as an example of what to do right, with its dense downtown housing, considerable green space and transit, which encourages walking and cycling.

But just getting rid of cars doesn’t fix things, either. Pedestrian malls have a high failure rate when cities simply close streets to vehicles. To succeed, there must already be a lot of pedestrians, and with shopping and restaurants to draw more. Buffalo, New York, helped revitalize its downtown by admitting cars into its pedestrian-transit mall. Jeff Speck worked with Oklahoma City, considered the “worst U.S. walking city,” to narrow the vehicle lanes, and add sidewalks, bike lanes and on-street parking. Tourism rose, while collisions and fatalities dropped.

It may seem to make sense that building more roads means faster commutes, but in reality, it’s the ideal way to make everything worse.


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