Hyde Park is a picture of health on a chilly winter morning.
Transport for London says carbon emissions in the zone are down by 16%
Joggers snake between dog walkers, cyclists race along the lanes on their way to work and horses canter through the trees.
But there's no escaping the roar of traffic along Park Lane and around Marble Arch.
It is bang in the heart of the newly-expanded congestion zone, now twice the size it was yesterday.
That traffic will remain, or even increase, because this particular route will stay free - a funnel to allow vehicles to run north-south through the heart of London.
But to the west of Marble Arch the new zone begins, and to the east the old zone remains in force.
'A solution without a problem'
From 7am motorists travelling into Bayswater, Notting Hill, Belgravia, Pimlico and Kensington have had to pay £8 for the privilege.
And while they may live in the most affluent parts of London - and Britain - many of them are unhappy about it.
The leader of Westminster Council, Simon Milton, says the new zone is "a solution without a problem. The level of congestion simply wasn't as bad as people make out".
Small businesses within the new charge zone are also bracing themselves for a negative impact.
Jane Morris, who runs an interior design company, says she expects her trade to fall by 20%. She also says her delivery drivers will have to spend £2,000 a year on essential journeys into the capital.
"We've got to spend more money on trains and the Tube. Then I think the people who don't have to go in cars will come out of their cars", she said.
"It's no good just penalising the motorist. The motorist always gets hit."
Given the recent uproar over the government's other scheme - road pricing - why such an apparently unpopular move?
Well, the Mayor of London Ken Livingstone believes the introduction of the first congestion zone in 2003 was a gamble that paid off.
And he reckons it's not as unpopular as some make out.
According to Transport for London, traffic levels within the zone have fallen by around 20%, the number of cyclists has increased dramatically, and hundreds of millions of pounds have been raised for public transport.
Carbon emissions, says TfL, are also down 16%.
Some of those within the congestion zone are happier for it too.
Julia Stephenson has lived in Chelsea for 15 years and recently gave up her car.
"It pretty much had to be surgically removed from me, but I haven't looked back," she said.
"There are far too many 'Chelsea tractors' where I live, and most of the time they're only carrying one person. I cycle instead now."
Brian Cook, from London Travel Watch, believes the changes don't go far enough.
He said: "We are concerned that the residents' discount will actually create more congestion in the existing zones. Residents can now go anywhere in central London for that 90% discount."
And not everyone is leaping from their cars.
One recent survey suggested three-quarters of motorists would rather pay the congestion charge than use public transport.
But there are plans to make the charge bite harder with a £25 tag for high emission vehicles like 4x4's - the much-maligned 'Chelsea tractors'.
Government figures put the increase in British road traffic over the past decade at 12%, and other local authorities have been watching the London experiment.
Ten have received funding from the government to investigate charging schemes.
And to those that complain about the inconvenience, Jim Footner of Greenpeace has a response: "Paying £8 or using other modes of transport is a small price for saving the planet."