Vishaan Chakrabarti is getting into a cab. This is a bit surprising because the architect and academic is a constant transit rider, like most of his neighbours in Manhattan.

"I'm a guy who's usually in the subway, unless I have a few calls to make," he admits good-naturedly as a fire truck screams past him. He thinks we should ride the subway, too – his new book, A Country of Cities, argues that "hyperdense" cities built around mass transit, make us more prosperous and happier, too.

"We're better off living in dense urban environments that are centred around mass transit," he says, after settling on directions with the taxi driver. "In the U.S., they're the most economically productive environments; they're the most sustainable environments; and they're the most socially mobile environments."

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He's not alone in making such arguments. In the world of urbanism and planning, there's been a barrage of recent books on similar themes – The End of Suburbia, The Triumph of the City, Cities are Good for You. But Mr. Chakrabarti has written maybe the most useful one, a polemic in favour of city living that makes the stakes clear.

He argues for more development with "hyperdensity" – enough population density to support subway lines. America, he writes, should try to remake itself as a nation with populous, walkable neighbourhoods, rural land and nothing in between. This means building mass quantities of affordable urban housing; funding subways, light rail and high-speed rail, and new schools and public buildings; cutting back tax breaks for home ownership and reducing spending on roads and highways.

Eventually, the typical American would live in "a transit-based, multi-centred" city "similar to contemporary London." They would be living in a much more sustainable way. They'd have more time to spend with family; they'd be healthier; they'd be happier, living with good transit, work and cultural amenities close by, and no highway driving necessary.

All this could happen with low-rise but dense development on the scale of, say, Montreal's Plateau district.

It's a radical vision. Today three-quarters of Americans live in car-oriented suburbs and, according to census data by Queen's University urban planner David Gordon, about two-thirds of Canadians do, too.

When he appears in Toronto next week, Mr. Chakrabarti will be debating author Robert Bruegmann, whose book Sprawl: A Compact History argues for the virtues and the necessities of suburbs – which are still very much here, and growing.

But Mr. Chakrabarti's arguments reflect a momentous change that is gearing up America and here, too: Economics and culture are pushing more of us to live in places where we can walk and take transit. It took a half-century of change to establish today's suburbs. Now the change is starting to go the other way, and Mr. Chakrabarti's book helps us understand where we'll land in another few decades.

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What do cities have to offer, for all the expense and tradeoffs they require? For one thing, economic opportunity. Working with American stats, the numbers are startling: 3 per cent of America's land mass, basically the cities, generates 85 per cent of its economic activity.

The Chicago region alone (a tiny smudge on the map of the continent) generates more economic activity than most of the U.S. states. This is where jobs, and the opportunities to find better opportunities, lie.

Then there are lifestyle and health questions that make walkable cities more attractive. The old malaise of the city – pollution, the threat of crime, and racial and ethnic tension – "has all but dissipated" in the 21st century, he says. At the same time, life in the car-oriented suburbs is less pleasant than it used to be. Traffic congestion, higher gas prices and an increasing awareness that driving everywhere is bad for you. City dwellers are healthier.

And then there is the desire to live more sustainably. There is no question, as Mr. Chakrabarti says, that the densest cities provide the smallest carbon footprints. City dwellers have smaller footprints than those who live in exurbs or rural areas: They travel shorter distances, live in attached houses or apartments, drive cars less often, walk more.

Mr. Chakrabarti, who is a principal at the brilliant, innovative firm SHoP Architects and teaches real estate at Columbia University, is both idealistic and pragmatic. He's hoping that public investment and good, innovative urbanism and design could really change the world. And this will require huge political change. "It's not about every site being New York or Hong Kong," he says. "People could still choose whether they want to live in suburbs, but we would see more investment from governments that would build on what is already a very strong demographic trend."

Indeed, his general point of view is strong among young people. "Millennials are showing a stubborn resistance to living in suburbs," as he puts it. There's no doubt that this is correct – young Canadians and Americans are less likely to own cars and have driver's licences. The most valuable city real estate today, according to a recent report from the Brookings Institution, is in places that are walkable.

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The conversation is changing. Ken Greenberg, a distinguished Canadian urban designer, points out that on the vanguard, the Vancouver and Toronto condo booms are drawing young people who have radically unconventional attitudes about living space, stuff and getting around. "Among people who live in downtown Toronto, 46 per cent walk to work," he says. "Not cycle, not take transit … just on foot." On the other hand, most new development growth is still in car-oriented suburbs.

"It's like turning a battleship," says Mr. Greenberg. "It's a very interesting, volatile time, with both things going on at once. The shift is happening, but we are still producing the old paradigm on autopilot."

On paper, Canadian governments – especially in Ontario, the capital of sprawl – espouse many of the goals shared by Mr. Chakrabarti and other city partisans. And yet, as Mr. Greenberg argues, "We're not going to walk away from all that suburban development we created in the last couple of generations.

"From St. John's to Vancouver, talk to planning directors in all those cities, and they tell you about two things they're doing simultaneously: one is the in-fill and repopulation of all the centres, and the second thing is, they all have plans for introducing improved transit and intensification along the transit lines in the suburbs."

Making that work, Mr. Greenberg argues, is the big challenge for the next generation. Before Canadians all become city dwellers, it's time to recognize that we are a suburban people – and that some new transit would be good for us.

Alex Bozikovic is The Globe and Mail's architecture columnist.