Beset by worrisome smog, Paris on Monday will ban half of all personal vehicles from the streets, Mayor Anne Hidalgo said Saturday.

Only cars with odd-numbered plates will be allowed on the streets unless they are carrying more than three people. Electric and hybrid vehicles will still be permitted regardless of plate number, as will, of course, emergency vehicles. As for those who will be forced to leave their cars at home, public transit in and around the city will temporarily be free.

Last March, Paris imposed a similar one-day ban on half the city's cars. The new ban comes after the city's air pollution spiked high enough last week to (briefly) become the worst in the world. Jon Terbush