An urban planning expert says town planners can learn a lot from the slums of Rio de Janeiro when it comes to building our future cities.

John Norquist, the president of the United States Congress for New Urbanism, is in Brisbane for the City of the Future Conference.

The former mayor of Milwaukee says population growth means high-density living will be the way of the future in Australian cities like Brisbane, Sydney and Melbourne.

Mr Norquist points to Rio's favalas as examples of functional communities and says the informal arrangements made in slums are a good model for how councils can improve zoning laws.

"To give you an example of where you have a very strict plan like the capital of Brazil, Brasilia, where most of the streets are grade separated and everything is use separated and it's planned on the utopian model that was predominant in the 1950s," he said.

"The capital of Brazil is one of the most lifeless places on earth. The restaurants and the nightclubs and so forth that you find in Rio you don't find that in Brasilia - you find it in the slums around Brasilia.

"So planners need to learn from the way human beings arrange their lives informally when there's not a plan."

Mr Norquist says planning cities with transportation and sustainability in mind is the "convenient remedy, the inconvenient truth".

He says Australian cities had it right before World War II, but since then, planning has led to urban sprawl, which means people are forced to rely on cars more.

"The pre-World War II development was built compactly and around transit," he said.

"In the post-war period there was a time in Australia - not quite as long and as devastating as what happened in the US - where you experienced a lot of sprawl."

Mr Norquist says urbanism does not mean the end of owning a car and having a backyard barbeque.

"There is an understanding in the real estate market in the US more and more that urbanism has a value, that urbanism creates a lot of variety of choices," he said.

"Even in our most suburban areas on the edge of metropolitan areas there's talk about building village centres that are walkable, where people can enjoy life, where they can meet their friends and have a social function and also market function, retail.

"The idea of just having a community built around cars with the main feature being giant roads and parking lots, that's not enough to people anymore. They want more than that."

In the United States there are between 35 and 40 million new homes expected to be built in the next 30 years and Australia is set to follow a similar path.

Mr Norquist says Vancouver in Canada - a city of boulevards and good transit - is a perfect model for Australia's major cities.

"It has no expressways at all and it's quite successful.

"It's been the most successful city in Canada in terms of property value growth, it's gained in population but the population seems very satisfied with the growing density of the city.

"It's a great tourist city, it's a great economic city, it has manufacturing, it has all kinds of things that makes for a great city."