Public transport was free in Paris today and half of the city 's cars were forced off the road in a bid to fight pollution . In a radical move which will be studied in other European capitals like London , French Socialists said everything had to be done to make air cleaner . Anne Hidalgo , the mayor of Paris , said : ' I am delighted the state has agreed to put in place a partial driving ban on Monday , which I have been requesting for several days . ' Scroll down for video . Public transport was free in Paris today and half of the city 's cars were forced off the road in a bid to fight pollution . Only vehicles with number plates ending in an odd number were allowed , with exemptions for taxis , electric cars and ambulances . Authorities were planning to ban cars with even numbers on Tuesday , but the scheme was halted following improving forecasts . Foreign visitors to Paris , including thousands of Britons on holiday , were also permitted to use their cars . But police patrols were seen booking locals who flouted the ban , forcing them to return home . Meanwhile , Metro trains and buses were full to overflowing as thousands abandoned their vehicles . 'There are horrific crushes on the trains , ' said Jean Babin , a 43-year-old commuter from the suburb of Juvisy , who usually travels to the city in his Renault . 'Free transport is a great idea in principle but it can potentially cause a number of problems of its own , and you do wonder who is going to pay for it all ' . Air quality monitors showed concentrations of potentially dangerous particulates in the Pars air were above the recommended maximum . Only vehicles with number plates ending in an odd number were allowed , with exemptions for taxis , electric cars and ambulances . Police patrols were seen booking locals who flouted the ban , forcing them to return home . Meanwhile , Metro trains and buses were full to overflowing as thousands abandoned their vehicles . These are created by cars and lorries , heating and heavy industry , and can potentially cause serious health problems . 'Due to the improving situation today and tomorrow , the alternative traffic ( plan ) will not be renewed Tuesday , ' announced Ecology Minister Segolene Royal , who took time to salute 'the good citizenship of motorists who understood the necessity of this measure . ' The Airparif monitoring agency said smog density was still near alert levels Monday , but rain forecast for Tuesday was expected to clear the air . Though public transport is free of charge to take the sting out of the restrictions , drivers in the capital have protested against the measure , despite it having been used only twice since 1997 . Paris area is confronting an increasingly troubling air pollution problem , caused by vehicles , heating and heavy industry . Similar emergency restrictions were last implemented almost exactly a year ago - on March 17 - during a particularly bad spike in the pollution levels . Paris area is confronting an increasingly troubling air pollution problem , caused by vehicles , heating and heavy industry . Authorities measure the concentration of particulates with a diameter of less than 10 microns - so-called PM10 - in the air to determine pollution levels . The safe limit for PM10 is set at 80 microgrammes per cubic metre ( mcg/m3 ) , with levels in Paris Monday expected to be somewhere between 40 and 55 mcg/m3 . The city 's alert level is fixed at 50 mcg/m3 . According to a 2011 World Health Organisation report , the planet 's most polluted city was Ahvaz in Iran with an average of 372 mcg/m3 . Beijing had an average of 121 mcg/m3 , while Paris was measured at 38 mcg/m3 .
Only vehicles with number plates ending in an odd number were allowed . French Socialists said everything had to be done to make air cleaner . Foreign visitors to Beijing - including Britons - permitted to use their cars .