Mexico City is presented as a cautionary case in the debate over how cities should manage traffic and pollution. A weekday driving ban keyed to the last digit of a car’s license plate restricted individual choices directly, but the book says it did little to reduce traffic: some drivers bought second cars, while those still permitted to drive had no incentive to find alternatives. The contrast with Singapore’s congestion pricing turns the city into evidence for a broader argument: rules that price road use can leave the decision to drive with individuals, whereas categorical restrictions may invite workarounds.

The License-Plate Rule

The policy was adopted in an attempt to curb air pollution. It assigned different weekdays to cars according to the last digit on their license plates: a plate ending in 5 or 6 meant no driving on Monday, 7 or 8 barred driving on Tuesday, and 3 or 4 barred it on Wednesday. Everyone could drive on Saturday and Sunday. The arrangement regulated access by schedule rather than by charging for the use of a congested road.

Adaptation and Limited Effect

The book identifies two reasons the restriction did not do much to reduce traffic. First, drivers could still use their cars on six days of the week and therefore had little incentive to find alternatives for those days. Second, many Mexicans bought additional cars that could be driven on their assigned off days. The policy’s formal limit thus produced a practical workaround: it constrained a particular vehicle on a particular day without necessarily changing a household’s ability or willingness to drive.

Contrast with Congestion Pricing

Mexico City’s system is contrasted with Singapore’s pricing plan. Singapore charges drivers to enter designated zones and, rather than forbidding particular people to drive on particular days, makes the cost of driving visible and leaves the choice to each driver. In the book’s account, the combined effect of those individual decisions is trusted to help manage traffic. The comparison does not present Mexico City as a detailed portrait of the city itself; it uses the license-plate restriction to distinguish direct prohibition from a price signal, and to show how a policy can be undermined when people can adapt without changing their driving behavior.