"Access around Central is like a rabbit warren. What this will do is open it up,"Transport Minister Andrew Constance said.

"Look at Grand Central Station in New York – this is what we're going to see here in the heart of mid-town in terms of Sydney."

One commercial property will be compulsorily acquired for the new walkway,and as well as a number of leases at the station.

The government has called for expressions of interest from the private sector for the fitout of the station and the new Central Walk on Wednesday.

A bridge will also be built from Regent Street,on the western side of the station,to the construction area at Central.

Sydney Trains chief executive Howard Collins described the plans as a"massive game changer"for people who had difficulty getting around the station.

"It will just make interchanging so much easier,"he said.

Timetable changes to be released next year for Sydney's rail network will incorporate the first stage of the new metro line from Rouse Hill in Sydney's north west to Chatswood,as well as the impact of the temporary loss of the three platforms at Central during construction.

Mr Collins urged people to be patient during construction of the walkway and new metro platforms,and said staff would help people navigate the building site and ensure every existing service continued to operate.

"We're not cancelling services but there may be some changes in your route and your pattern of service,"he said.

The station for the metro line beneath Central will be 250 metres long and sit 30 metres below the surface.

In September,the government sought community feedback on plans to renovate the 110-year-old Central Station,which covers 20 hectares.

An"outcome report"of that feedback is understood to focus on the need for more shops,cafes,restaurants and bigger spaces.

The station's overhaul will be a key part of the redevelopment of the Central to Eveleigh rail corridor.