Query: How many days a week does the city encourage people to go without a car?
Context: To clean up pollution, the federal and local governments implemented numerous plans including the constant monitoring and reporting of environmental conditions, such as ozone and nitrogen oxides. When the levels of these two pollutants reached critical levels, contingency actions were implemented which included closing factories, changing school hours, and extending the A day without a car program to two days of the week. The government also instituted industrial technology improvements, a strict biannual vehicle emission inspection and the reformulation of gasoline and diesel fuels.