Hundreds of police officers monitored the traffic passing through Paris on Monday after high levels of pollution caused concern and so major restrictions were introduced by the French government.

The restrictions on Monday meant that only motorists with odd numbered number plates where allowed to drive. Due to this success those with even numbered number plates were allowed to travel on Tuesday.

Ministers acted after air pollution exceeded safe levels for five days running in Paris and surrounding areas.

Environmental research showed that the lower traffic levels on Monday had improved the smog significantly that was looming over the city the past few weeks. The smog was caused by changes in the weather which stopped the pollution from dispersing.

Motorcycles were also covered by the ban, which ran from 4am to midnight. There were some exceptions to this ban which were taxis, electric vehicles and vehicles carrying more than three passengers. Those motorists who did not abide to the rule faced a small fine.

About 700 police ran nearly 180 control points around the Paris region, correspondents say, handing out tickets to offenders. Police were reported to have ticketed nearly 4,000 people by midday on Monday, and 27 drivers had their cars impounded for refusing to co-operate with officers.

On Friday, public transport was made free of charge for three days in an attempt to encourage people to leave their cars at home.