The most direct (and arguably only) way to reduce metro area traffic is by charging a price for congestion. Drivers may not initially like it—although surveys show they come around—but they do immediately respond to it. Jonas Eliasson illustrated that point during a TED-x talk on the Stockholm pricing program he co-designed: on the left is a rush-hour traffic jam the day before its implementation; on the right are empty roads the day it took effect:
The reverse scenario is also true, as a new study of Milan’s road pricing program reveals. In late July 2012, an Italian court called an abrupt and unexpected halt to the city’s congestion cordon, known as Area C, which cost 5 euros to enter from 7:30 a.m. to 7:30 p.m. The ruling caught people by surprise, since similar lawsuits had failed, so when the charge was suspended the next day you might have expected a lag before drivers rushed back to the rush-hour roads.