Technology entrepreneur Elon Musk has hinted interest in helping solve Sydney's road congestion nightmares, quoting $1 billion on Twitter for a high-speed transit tunnel through the Blue Mountains.

Key points: The 50-kilometre tunnel would link the Penrith and Lithgow regions

The 50-kilometre tunnel would link the Penrith and Lithgow regions Passengers would be transported at high speeds in an electric vehicle

Passengers would be transported at high speeds in an electric vehicle Elon Musk says it could be built for about $1 billion

The bold idea was floated by independent NSW MP Jeremy Buckingham.

People would not actually drive through the tunnel — their vehicles would be secured on platforms that can travel at high speeds between stations.

Mr Buckingham pitched it to the Tesla boss on Twitter by explaining Sydney was "choking with traffic".

"How much to build a 50km tunnel through the Blue Mountains and open up the west of our State?" he tweeted.

Mr Musk replied it would take about $15 million per kilometre for the two-way tunnel, with an additional $50 million per station, taking the project to an estimated $1 billion.

Loading

Mr Buckingham said commuters would access the tunnel by driving electric vehicles into the station before being transported via elevator into the tunnel.

A special vehicle would then transport them at high speeds between stations.

A similar tunnel system is being tested in Los Angeles where cars are lowered into the tunnel on a lift before being moved through it on platforms at high speed.

Another is under construction in Chicago.

Mr Buckingham tweeted an image of the potential tunnel route. ( Supplied: Jeremy Buckingham )

Mr Musk was not the only one to reply to the proposition.

Australian billionaire Mike Cannon-Brookes described the move as "a bargain for Sydney".

Mr Buckingham, who was once a councillor with Orange City Council, said the transport loop would be "the envy of the world" and benefit regional cities.

"You could live out in the beautiful western region of NSW, enjoy the lifestyle, clean air and national parks while commuting into jobs centres of Penrith and western Sydney," he said in a statement.

"The infrastructure plan takes the pressure off traffic congestion and resources in Sydney, while providing a lifeline for our regions."

The NSW Farmers' Association said it was delighted to see "its" idea for the Blue Mountains tunnel grab the attention of two of the world's tech billionaires and urged NSW MPs to look into it.

"One of the biggest challenges to growing the state's food economy is the inadequate east-west transport connections between the food bowl that is western NSW and Sydney," president James Jackson said.

Passengers would access the loop via elevator and travel on special platforms. ( Supplied: Jeremy Buckingham )

Mr Buckingham said he would focus on the plan as he seeks re-election and called for the Premier and Opposition Leader to meet with Mr Musk to discuss it.

It is not the first time Mr Musk has flagged interest in a major Australian project on Twitter.

In 2017, he used the platform to declare his company could install a battery capable of "fixing" South Australia's power problem within 100 days — or do it for free.

He followed through, constructing a giant lithium ion battery after partnering with Neoen and beating more than 70 competing bids in a government procurement process.

That project came about following a challenge from Mr Cannon-Brookes, who tweeted to Mr Musk offering to "make the $ happen (& politics)" if it was running within 100 days.