On Monday, drivers of older gas and diesel cars in Britain were hit with new fees if they want to drive those cars into the city center in London.

The new emissions charge of 12.5 British pounds ($16.30), follows similar charges on older vehicles in Paris, although it so far applies only to the same 8-square-mile area as London's central congestion zone. Driving such an older vehicle into the central zone will subject owners to the new emissions charge on top of the existing congestion charge, for a total of up to $31.50 a day. Drivers who don't pay can be subject to a $131 fine per instance.

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The money is set to fund improvements to the city's public transportation network. Unlike the city's congestion pricing, the Ultra-Low Emissions Zone pricing is in effect 24/7. Electric cars are exempt even from the congestion pricing.

It's unclear how much pollution the new Ultra-Low Emissions Zone might save. Frank Kelley, Professor of Environmental Health at King’s College London, told the London Evening Standard that, "I don’t think it’s going to be noticeable to the person in the street walking around, because you can’t see this pollution the majority of the time. So what you would have to do is look at the data which we collect through the London Air Quality Network. Over a longer term, when you look at these data trends, then you’re looking over years, and things going in the right direction.”

London Ultra-Low Emissions/Congestion pricing zone [Source: Transport for London]

London Ultra-Low Emissions/Congestion pricing zone [Source: Transport for London]

Initial estimates from Transport for London, the city's transit agency, suggest that the newer cars allowed in the zone individually produce 45 percent less pollution than the older cars that face the fines. 

Vehicles subject to the fines include pre-2006 gas cars, pre-2015 diesels including trucks and buses, and pre-2007 motorcycles. Cars registered as classics will be exempt, because they already pay a special tax on historic vehicles. In all, TfL estimates that it will affect 40,000 cars, 19,000 vans, 2,000 trucks, and 700 private buses.

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Residents of the zone can apply for a 100 percent exemption, good through 2021. Khan plans to implement a fund subsidizing the purchase of newer cars for the city's lower-income residents.

“Air pollution is a national health crisis, and I refuse to stand back as thousands of Londoners breathe in air so filthy that it shortens our life expectancy, harms our lungs and worsens chronic illness," said London Mayor Sadiq Khan, regarding plans to expand the zone. “We’re doing everything in our power to tackle this issue and are starting to see improvements in air quality with the wide-ranging action we’ve taken already on tackling the most polluting cars, and cleaning up our bus and taxi fleet."

Although the plan currently applies only to the same central-London congestion-pricing district, it calls to extend the zone to a 52.5 square-mile area bounded by London's North and South inner circle roads in 2021, when it may affect 138,000 vehicles.

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Two U.S. cities are also considering congestion pricing similar to London's. New York Governor Andrew Cuomo baked new congestion charges for Manhattan into the state's latest budget proposal, and they're set to take effect in 2021.

And the Los Angeles Metropolitan Transportation Authority, in the nation's car capital, also launched a plan to study congestion pricing on the city's gridlocked west side.