Choked Mexico City bans 1m cars in air pollution alert

Free public transport offered as city remains shrouded in muddy brown smog and officials consider suspending industrial activity

Authorities have banned more than 1 million cars from the roads and offered free subway and bus rides to coax people from their vehicles as Mexico City's first air pollution alert in 11 years stretched into a third day.

Officials advised people on Wednesday to limit outdoor activity owing to high ozone levels that were nearly double acceptable limits in the sprawling capital, which lies in a high-altitude valley ringed by smog-trapping volcanic mountains.