Sydney's highly congested rail corridor between Penrith, Parramatta and the central business district will be targeted with a $1 billion series of works in the next few years.

But the state government has been unable to provide much detail on what these works would include, and some of the other projects included in its $20 billion funding pitch for re-election are similarly vague and unscoped.

The promise of the Western Sydney Rail Upgrade was one element of a mammoth transport funding program announced by Premier Mike Baird on Tuesday, which includes promises of new motorways, light rail lines, bus ways and another rail crossing of Sydney Harbour.

The largest element in the funding program is a $7 billion boost for the next harbour rail crossing project which Mr Baird said he hoped to have under construction by 2017 and completed by 2024.

That project, which should cost more than $10.4 billion in total, will connect to the north-west rail link at Chatswood, run under the harbour and the city, and connect with the Bankstown Line at Sydenham.

The government has confirmed that as well as three new stations in Sydney's central business district and two new stations north of the harbour, it is looking at building a new station at either Sydney University or at Waterloo as part of this new line.

But the most congested rail corridor in Sydney is the Western Line between Penrith, Parramatta and the City, which has been targeted with a $1 billion Western Sydney Rail Upgrade program, also announced on Tuesday.

Government documents show the program will include new signalling systems, power supply upgrades, and will target "pinch points" on the rail network, but Transport Minister Gladys Berejiklian's office was unable to specify what these would be nor how they would work.

Another $600 million has been set aside for a light rail project near Parramatta, to go with $400 million already slated for western Sydney light rail, though the route of the tram line has not yet been determined.

And $300 million will be spent on rapid bus systems, potentially on Parramatta Road or Victoria Road.

The largest new project revealed by Mr Baird on Tuesday was a third road crossing of Sydney harbour, a tunnel between Rozelle and northern Sydney. But this project, first revealed in the Herald on Saturday, is not yet fully funded.

According to Infrastructure NSW, the advisory body which released its updated State Infrastructure Strategy on Tuesday, the "Western Harbour Tunnel" could cost about $4.5 billion. The advisory body has also proposed extending this new tunnel toward the Northern Beaches.

The western Sydney rail upgrade program was first announced by the government in mid-2012.

Ms Berejiklian said then that upgrading the Western Line and North Shore Line could mean that as many as 24 trains an hour could use these lines in the peak periods – compared to about 17 trains an hour that currently make it through these lines.

But there has been little discernible progress on these upgrade projects, nor clarity on what they would include.