Paris on Monday banned all cars with even number plates for the first time in nearly 20 years to fight sky-high pollution but opted not to extend the measure after an improvement in air quality.
The roughly 700 police officers deployed to man 179 checkpoints around the French capital to ensure that only cars with number plates ending in odd numbers were out on the streets.
By noon police reported that they had already issued 3,800 fines to motorists who had not respected the rules, among those 27 had their cars impounded due to their "behaviour" during the checks. Another 1,800 motorists had been issued tickets for various other driving offences.
The prefecture said the operation had gone "satisfactorily" and noted many people got off with a warning.
"There are people who take their car because they don't want to be pressed up against others in the metro. Today they will take a taxi."
The restrictions came into force across Paris and 22 surrounding areas from 5:30 am (0430 GMT). Bison Futé, a website the monitors taffic levels in the country reported there were half the number of traffic jams around Paris on Monday compared to a normal day of the week.
They will be reviewed on a daily basis, with odd numbers potentially banned on Tuesday if an extension is deemed necessary.
Parking will be free for vehicles with even number plates, the Paris Town Hall said, calling on residents to consult carpooling or car-sharing sites to work out their travel plans
However not everyone seemed to be aware of the ban, or chose to ignore it.
"You don't have the right to drive with your number plate," a man on a scooter remarked to another while stopped at a red light.
"Oh really? I didn't know," the second driver replied before speeding off. Those who choose to brave the ban risk a fine of €22 ($30) if paid immediately, or 35 euros if paid within three days.
Electric and hybrid cars will be exempted from the ban as well as any vehicle carrying three people or more.
It is the first time since 1997 that the French authorities have resorted to such a drastic measure.
The government made the announcement on Saturday after pollution particulates in the air exceeded safe levels for five straight days in Paris and its environs.
One enterprising website did not waste any time cashing in on the restrictions. Lending site e-loue.com encouraged Parisians with odd-number plates to rent them to neighbours who could not drive on Monday.
Ban is 'hasty, ineffective'
The issue has become something of a political football, with less than a week to go before key municipal elections.
The opposition UMP candidate for Paris mayor, Nathalie Kosciusko-Morizet, called the measure a "fig leaf".
Ecology Minister Philippe Martin said he understood the "difficulties, the irritation and even anger" over the move, adding: "But we just had to take this decision."
Martin said similar measures in 1997 "had yielded results," adding that he hoped that the number of vehicles on the roads would be "significantly lower" on Monday, without giving a figure.
The measure is also expensive, with free public transport costing the RATP - the state-owned Paris train, subway, tram and bus operator - €2.5 million a day, according to RATP head Pierre Mongin.
(To see what the pollution looks like check out this video below)
France's Automobile Club Association (ACA), which counts some 760,000 members, denounced the move as "hasty, ineffective" and "bound to lead to chaos".
"This measure had no effect in any country where it was introduced," said ACA head Didier Bollecker.
"Drivers are being targeted even though heating is more polluting, but no one is asking for heating to be used on alternate days."
By Saturday the number of pollution particulates in the air had fallen slightly after hitting a high of 180 micrograms per cubic metre - well over double the safe limit - on Friday.
So-called PM10 particulates are created by vehicles, heating and heavy industry, with the safe limit set at 80 per cubic metre.
The smoggy conditions have been caused by a combination of cold nights and warm days, which have prevented pollution from dispersing.
The pollution particulates in the air can cause asthma attacks as well as respiratory and heart problems.
The World Health Organization has said finer particulates - known as PM2.5 - are cancer-causing.