Media playback is unsupported on your device Media caption Sit in on a driving lesson in the American roundabout capital, Carmel

A roundabout revolution is slowly sweeping the US. The land of the car, where the stop sign and traffic light have ruled for decades, has started to embrace the free-flowing British circular.

A few moments after entering Carmel, it's clear why the city has been described as the Milton Keynes of the US.

As the sat-nav loudly and regularly points out, there's often a roundabout up ahead.

But unlike in the English town famous for them, driving into this pretty city on the outskirts of Indianapolis also involves passing several more under construction.

We are saving thousands of gallons of fuel per roundabout per year Mayor of Carmel, Jim Brainard

The city is at the forefront of a dizzying expansion, across several American states, of the circular traffic intersection redesigned in 1960s Britain and then exported globally. About 3,000 have been built in the US in the last 20 years.

The Mayor of Carmel, Jim Brainard, has become America's evangelist-in-chief on the matter, demolishing 78 sets of traffic lights and replacing them with those round islands so familiar to drivers in the UK. Four more will be finished in the coming months.

"We have more than any other city in the US," he says, standing proudly in front of one. "It's a trend now in the United States. There are more and more roundabouts being built every day because of the expense saved and more importantly the safety."

He quotes a study by the Insurance Institute for Highway Safety which suggests there is on average a 40% decrease in all accidents and a 90% drop in fatal ones when a traffic intersection is replaced by a roundabout.

The long-term financial saving is about £150,000, he says, due to reduced maintenance costs, and there are also fuel savings.

"Not just the cars that aren't idling at traffic lights, but starting from a dead stop takes up more fuel also, so we are saving thousands of gallons of fuel per roundabout per year," says the Republican mayor.

"And aesthetically, we think they're much nicer. If one is looking out their living room window, would you prefer to see a blinking traffic light all night or a beautifully landscaped roundabout with a fountain and flowers?"

Roundabouts v Rotaries The modern roundabout gives way on entry and priority to cars already on it

They are usually smaller than rotaries

And vehicles usually travel at lower speeds

Rotaries may have traffic lights and stop signs

Marble Arch in London and the Arc de Triomphe in Paris are found on rotary systems

The mayor's unlikely passion began while studying in the UK, and his strong Anglophile credentials are in evidence from a glance around his office - a book by Prince Charles entitled Vision of Britain lies on the coffee table.

"I remembered those roundabouts in England and it raised the question in my mind - why don't we do this? I remembered they worked better than traffic lights so I started to do a bit of research and convinced my traffic engineers to try some."

There was scepticism at first, he says, but public education is critical and there was a newsletter and video campaign to tell people about the safety and environmental advantages.

Before every roundabout, there are squiggly lines on the road and on roadside signs to warn drivers which lane they need to be in.

The mayor's ambition is to replace the city's remaining 43 traffic lights too, apart from one. The traffic lights on the corner of Main Street and Range Line Street will survive - not because a plaque at the spot claims the country's first automatic traffic signals were installed here in 1923, but the street's just too narrow to fit a roundabout.

Leading roundabout states Washington

Colorado

California

Florida

Kansas

Oregon

Maryland

Indiana

Wisconsin

Arizona

The ornate fountain roundabouts of Carmel are a far cry from the large, one-way rotary systems conceived in the US and in Europe in the early 20th Century but which largely fell out of favour due to congestion problems.

Then forward-thinking British traffic engineers like Frank Blackmore tinkered with the designs and the UK established the modern roundabout by introducing a mandatory "Give way" rule for cars entering.

The US still has the older versions, called rotaries or circles, notably in New Jersey and Washington DC. But they remain quite unpopular, a confusing sprawl of signals, stop signs and concentric lanes.

The simpler British version is thought to have first arrived in the US in 1990, in Nevada, and it is these which are now proliferating. California has built nearly 200 in the last two or three years.

Countries with British-style roundabouts (selected) France (has about 30,000, the most in the world)

Australia

New Zealand

Thailand

Italy

Belgium

Iraq

Jordan

The problems Americans have navigating them was satirised in the film European Vacation starring Chevy Chase, who takes his family sightseeing in London but gets stuck until nightfall on a roundabout next to Big Ben.

There is some truth in that caricature. Some drivers in Carmel have been known to wait for the whole roundabout to clear before entering, says driving instructor Mike Ward, but learners soon get used to them.

Police in the city say there are accidents on them, often caused by confusion or unfamiliarity, but they are much fewer and less serious than at a traffic light.

The people of Carmel seem happy living in the country's unofficial roundabout capital. The mayor, who has made roundabouts a central plank of his manifesto, is on the verge of earning his fifth term in office.

Image caption Roundabouts in Carmel have to look good

"I think they're awesome," says Blair Clark, who has lived in the area for 26 years. "They keep the traffic flowing, you don't have to stop, you save gas and there are less accidents."

Another driver, filling up his gas tank, says: "We're proud of our city and proud of our roundabouts."

But beyond Carmel, there has been greater resistance to them. One newspaper columnist in Atlanta says this undesirable European import will lead to higher taxes and accidents.

And Dan Neil, motoring correspondent at the Wall Street Journal, personally welcomes their arrival but thinks there is something deep in the American psyche which is fundamentally opposed to them.

"This is a culture predicated on freedom and individualism, where spontaneous co-operation is difficult and regimentation is resisted.

A UK view of US roundabouts well landscaped

lower speeds

better for cyclists and pedestrians Clive Sawers, British traffic engineer who has advised US cities on roundabouts

"You see it in the way Americans get in line, or as the Brits say, queue. We don't do that very well.

"Behind the wheel, we're less likely to abide by an orderly pattern of merging that, though faster for the group, may require an individual to slow down or, God forbid, yield."

Americans tend to be orthogonal in their thinking and behaviour, he says.

"We like right angles, yes and no answers, Manichean explanations. Roundabouts require more subtlety than we're used to."

Un-American or not, it's only a matter of time before they are covering every US state, says Gene Russell, a leading civil engineering professor at Kansas State University.

So while the Americans gave the British fast food, rock and roll and baby showers, in return they get free-flowing, circular traffic intersections. A fair cultural exchange?