Road congestion in Australian cities, if left unchecked, could cost the economy $20.4bn by 2020, according to a new report.

Federal Infrastructure Minister Anthony Albanese, while releasing the State of Australian Cities 2010 report, said productivity growth in Australia’s 17 cities with populations greater than 100,000 was critical to the economy.

“Over half of Australia’s economic activity occurs in Sydney, Melbourne and Brisbane, with a further 15% in Perth and Adelaide,” Albanese said. “Urban congestion is a major handbrake on productivity.”

The use of cars in cities has increased thirty fold since 1950 and has replaced rail as the main mode of passenger transportation.

Unfortunately road infrastructure, especially in major cities, has not kept up with this rate, which is growing faster than the population.

The report also said freight traffic in Australia’s eight capital cities was expected to grow by 70% between 2003 and 2020.