How different cities responded to December's winter smog

Paris introduced free public transport; Madrid restricted cars; Londoners were advised to take less exercise

Winter smog returned to our cities in December. Modern smog is less visible than Victorian pea-soupers but a thin brown layer could be seen on the horizon as still weather trapped the air pollution.

Paris had ten days of smog at the start of the month; the worst pollution for a decade. Emergency actions to reduce the health impacts included free public transport, reduced traffic speeds, lorry bans in the city centre, a ban on wood burning and four days of alternating bans on cars with odd or even number plates.