"There was no room for people and there was lots of room for cars," said Mr Gehl on Wednesday. "Part of it is still in that situation but other parts are now being turned around, which is a great joy to see."

Mr Gehl, whose study a decade ago – Public Spaces Public Life – has helped form the basis of Lord Mayor Clover Moore's vision for Sydney's core, has been in town this week to receive the keys to the city.

In his work for Sydney, Mr Gehl, who has travelled the world evangalising for the "Copenhagenisation" of urban spaces, advocated wider footpaths, a light rail line down George Street and the progressive greening of the city.

In the decade since, he says, he's been impressed by Sydney's growing network of bike lanes. He was also cheered by the removal of the noisy and functionally useless Monorail.

And he is hopeful about the changes to George Street prompted by the construction of light rail. However, like Cr Moore, Mr Gehl is concerned the state government may undo its good work with the final designs of the project.

"There has been seemingly a drift from light to heavy, from small trains to larger and larger trains, from small stops to longer and longer stops," said Mr Gehl, who is the second Danish architect to receive the keys to the city, after the Opera House's Jørn Utzon.

"Really the whole exercise in George Street, which is a rather narrow street with hopefully many trees, is to make it a very elegant beautiful state-of-the-art main street," he said.

Mr Gehl is worried about the government's plans for large shelters at tram stops.

"If too much new clutter goes in … and you can't see the sky for too much roofing, then some of the elegance and some of the purpose of the whole exercise goes sky-high."

Mr Gehl, 80, has worked in dozens of cities across the world, and has consulted in Perth, Adelaide and Melbourne.

One singular feature of Sydney's urban politics is the continuing tetchiness of the relationship the state and local government.

"We could not fail to notice that the city and the state has not been working on the same pace and with the same goals," he said.

"There has been so much nitty-gritty bickering and whatever. I really have the feeling that city really have had, and still have, a strong wish to go places but … they have to wait for the state to be mature enough to do what the other cities have done."

Mr Gehl said a further change needed was the eventual removal of the Western Distributor from the surface of the city.

"That's why we suggest that when it crumbles it should be taken down and that an underground link to the other side of the bay be organised," he said.

"This is being done in city after city after city."

Cr Moore said many of Mr Gehl's recommendations had been implemented, "from simple initiatives that make our streets more liveable, like upgrading street furniture and planting more trees, to major projects currently underway, including the transformation of George Street and laneways throughout the city centre".

"I'm immensely proud of this work bringing Jan Gehl's ideas to life," she said. "Sydney is richer for his vision and expertise and we are delighted to award him the key to what is now a truly global city."