By Ryan McGreal
Published November 24, 2008
The Boston Globe has an intriguing investigative piece on Boston's "Big Dig" underground expressway, which, despite reconnecting the North End with downtown, has had the opposite of its intended effect on traffic:
While the Big Dig achieved its goal of freeing up highway traffic downtown, the bottlenecks were only pushed outward, as more drivers jockey for the limited space on the major commuting routes.
Ultimately, many motorists going to and from the suburbs at peak rush hours are spending more time stuck in traffic, not less. The phenomenon is a result of a surge in drivers crowding onto highways - an ironic byproduct of the Big Dig's success in clearing away downtown traffic jams.
This is a straightforward example of induced demand, in which more people choose to drive longer distances more often when it becomes easier to drive.
Paradoxically, cities that expend the most resources to accommodate traffic tend to suffer the most traffic, longest commutes, highest overall levels of air pollution, and so on.
The Globe continues:
Carrie Russell, staff attorney for the Conservation Law Foundation, said the Globe analysis of commuter times shows "we can't pave our way out of congestion."
"Adding more traffic lanes only attracts more people to highways and the roads leading to those highways," she said.
This and other examples of induced demand offer lessons for cities like Toronto with similar elevated highways cutting through their downtowns. The idea of pulling down the Gardiner Expressway has been kicking around for a long time.
The latest recommendation would replace the Gardiner with a ten-lane Lakeshore Boulevard to preserve highway capacity. Perhaps it makes more sense to reduce that lane capacity, increase transit capacity (particularly the GO Lakeshore line) and try to reverse some of the induced demand that has commuters crawling down the QEW.(Hat tip to Treehugger for finding this.)