It is the city's busiest transport corridor - each year motorists rack up 9 million kilometres on the 10km-long asphalt avenue.

Sydney may be regarded overseas as a hedonist's paradise of sunshine and surf, but local lore has it that the average inhabitant spends more time stuck in traffic on Parramatta Road than lounging on the golden sands of Bondi Beach.

The bleak corridor of exhaust fumes and cracked concrete was once described by an urban planning academic as 'not just a bad road; a notorious emblem of all that is ugly, abrasive and frustrating'.

So the announcement this week that the state government intends to build a sleek Hong Kong-style subway system linking the city and Parramatta was welcomed by harassed commuters.

New South Wales state premier Morris Iemma said the system would be modelled on Hong Kong's MTR and the MRT of Singapore.

The aim is to tempt thousands of commuters out of their cars in favour of travelling to work in air-conditioned comfort in swift, almost silent trains. Each six-carriage train will be able to carry 1,000 people, with 30,000 passengers an hour being whisked in and out of the central business district.

It will be the first stage of a mass transit plan that will eventually extend way out west to satellite centres such as Penrith and Blacktown, and deep into the eastern suburbs, linking Maroubra and Botany Bay.

'It's not if Sydney gets a metro, it's when,' said Mr Iemma. '[Services will be] high frequency and provide an alternative to heavy rail.'

The project, expected to cost between A$5 billion (HK$35 billion) and A$7 billion, is to be paid for by selling off three state-owned electricity companies and leasing out power stations - a deal expected to earn the government A$15 billion.

The subway could take 'many decades' to build, Mr Iemma said. 'What I'm about is getting cracking on starting metros. They're not going to happen overnight.

'They take many years to build, but ... a decision has been made, we will have metro for Sydney.'

The exact cost, the construction time and the first route to be built would be revealed early next year, he added.

Sydneysiders may be forgiven, however, for being reluctant to throw away their car keys.

They have become wearily accustomed over the years to seeing promises of shiny infrastructure projects come to nothing.

A decades-old commitment to extend the existing overland rail network to Bondi Beach remains unfulfilled, and as recently as 2001, rail planners told the state government that three metro lines needed to be built by 2020.

State opposition leader Barry O'Farrell indulged in a spot of predictable point scoring, but his criticisms held some truth.

'Morris Iemma's claim that funds raised from any electricity sale would be used to renew state infrastructure simply can't be believed given Labor's history and its failure to deliver a long list of projects over 12 years.'

Frustrated commuters inching their way along Parramatta Road will await future developments with interest.