- Across pollutants and specifications there is no evidence that the program has improved air quality. The policy has caused a relative increase in air pollution during weekends and hours of the day when the restrictions are not in place, but there is no evidence of an absolute improvement in air quality during any hour of the day or any day of the week. Furthermore, while it was hoped that the program would cause drivers to substitute to low-emissions forms of transportation, there is no evidence of increased ridership of the Mexico City subway or public bus system. Instead, evidence from the market for used taxis suggests that the program induced substitution to taxis.
ėJust take their keys!î
There are probably quite a few enviros and transit-backers who wish we'd stop asking people to drive less, stop talking about tinkering with the gas tax, and just yank keys away from drivers. Mexico City tried that, sort of. In 1989 officials introduced a program that bans all vehicles from driving one workday per week based on the last digit of the vehicle's license plate. Certainly that kind of "get tough" policy would cut emissions and boost transit ridership ... Or maybe not. Matthew Kahn points to a study by University of Michigan's Lucas W. Davis: The Effect of Driving Restrictions on Air Quality in Mexico City. From the abstract: