Building more roads is not always the solution. More roads means more incentives to get to a place fast, so people will buy more cars, drive more frequently, and… cause more traffic jams. But more traffic jams, it will discourage taking the car as much, which reduces traffic jams. Which in turn makes people take the car more.
That is how complex it is to solve the problem of traffic jams in large cities and the busiest urban centers. A paradigmatic example of this took place in South Lake Union, near Mercer Street, in the United States: what was a boring little neighborhood of body shops and small local businesses, has been replaced by gigantic buildings of glass and steel that host the Amazon headquarters, as well as other tech companies.
Incentives and Jevons Paradox
Years ago, the city decided to invest $ 74 million to improve traffic flow in this area. The results, however, were not as expected. Mercer Mess only made the journeys two seconds faster than before. $ 74 million for two seconds didn’t seem like a smart investment.
However, given that the Mercer corridor now hosted 30,000 more cars than before the upgrade project, then it does seem like an interesting investment: despite the fact that there are many more cars, the travel time has not increased. It has even been reduced by two seconds.
Similarly, to measure the benefits of a project, we need to consider the consequences of improvement that it entails along all the routes in a specific area of the city, which is not so simple. In addition, as already mentioned, building more roads can also be an incentive for more cars to circulate, not less, which will lead to more traffic jams. This is known as Jevons paradox:
Something that also happens, by the way, with parking spaces. So how do we fix this? Not making more parking spaces, but reducing them little by little, as he points out Tom vanderbilt in his book Traffic:
From 1994 to 2005, Copenhagen cut the parking spaces in the city center from 14,000 to 11,500, replacing them with parks and bicycle lanes. Over the same period, and not by chance, bicycle traffic increased by about 40 per cent (a third of people commuting to work now do so by bike) and Copenhagen has become one. one of the few places in the world where one can read, in a report, a phrase that would seem like a comic typographical error almost anywhere else: “Cycle traffic is already so widespread that congestion on certain bicycle routes has become a Problem, as was the bike parking space.
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