Thousands of cars banned from roads as Mexico City chokes in longest pollution alert for two decades

Authorities in Mexico City have ordered cars off the streets and warned people about exercising outdoors as sprawling metropolis chokes in its worst smog for nearly two decades. Hundreds of thousands of less efficient vehicles have been banned from the roads in the Mexican capital, where a pollution alert has been in place since Monday. Ozone levels topped the 150-point threshold that typically triggers a smog alert for the following day again on Friday.