A comprehensive new study investigating east coast high-speed rail argues that it could be $30 billion cheaper than first thought and pay itself off entirely within 40 years.

The rail debate is back on track, with the Federal Government vowing to speak to the states about the project and to protect a future corridor for the network.

The Melbourne-Sydney flight route is the fifth busiest in the world and for decades governments have been discussing high-speed rail as a solution to ease the pressure on airports.

Clean energy group Beyond Zero Emissions (BZE) and the German aerospace centre came up with a model of a 1,799-kilometre route, linking Brisbane with Sydney, Canberra and Melbourne.

According to their timetable, it showed the journey between Sydney and Melbourne would take two hours and 55 minutes, while Sydney to Canberra would take about an hour.

It proposes peak speeds of 350 kilometres per hour.

The BZE report puts the capital costs of the network at $84 billion, compared to $114 billion estimated from the previous Labor government's high-speed rail study.

"It's a lot cheaper to run and a lot cheaper to build because of the reduction in tunnelling and bridge-building that's required in the route we've selected," BZE's chief executive Dr Stephen Bygrave said.

Researcher Gerard Drew says their proposed alignment has 44 per cent fewer tunnels and 25 per cent fewer bridges.

The proposed route for a high speed rail network linking Brisbane, Sydney, Canberra and Melbourne. ( Beyond Zero Emissions )

German experience paves the way

The German aerospace centre, known as Deutsches Zentrum für Luft- und Raumfahrt e.V (DLR), is the country's national centre for aerospace, energy and transportation research.

It has used Australia as a case study for building a next-generation rail network.

DLR's Simone Ehrenberger says it was more than just plotting points on a map.

"We did a quite detailed calculation of the actual routes of where the tracks are going within cities," she said.

"We considered the exact city access to the stations."

The man in charge of the country's project to build a next-generation train, Dr Joachim Winter, has thrown his support behind an east coast high-speed rail network in Australia.

"We think it's perfect because you have a concentration of large cities, but not so many people scattered around as Germany," he said.

He says Australia is in a great position to be building the network because it is virtually starting from scratch.

"To construct a high-speed railway is expensive, but it's not difficult because most of the problems have been understood," he said.

"[Australia] is a follower and in a better position than [Germany] had when we started to run this... without knowing everything about the consequences."

The European support has not just come from train researchers.

Senior officials like European Commission's deputy head of cabinet for transport, Keir Fitch, believe Australia should get on board as well.

Mr Fitch says it would be a smart decision for the east coast.

"You need to of course do the analysis properly, but where you've got passenger flows [like the ones between Sydney, Melbourne and Brisbane] then it should [make sense]," he said.

"Rail, particularly for densely populated areas has great benefits in that you can move people in and out of cities quickly and efficiently on it.

"You provide something which - all the experience we've had shows - is much more attractively certainly for getting people out of planes to trains, freeing up air capacity or simply reducing carbon emissions.

"You're not going to be able to do any of that with a road."

Expert says high-speed rail sums don't add up for Australia

The man who helped do the sums for the previous government's high-speed rail study says he understands the love for high-speed rail but that it just does not add up financially.

"The economics were not too bad - not great - but better than we all thought and that was because of the value of travel time savings compared to planes which have delays and so on," ACIL Allen Consulting's David Greig said.

"But the financial side was quite poor because you need to get revenue from those people who are getting a better service, and the study didn't find a way to do that, so although the economics were line ball, the return on investment was something like 1 per cent.

"Even just [building a network from] Sydney to Melbourne is $50 billion odd.

"Flipping through the newspapers one doesn't get the impression there's a spare $50 billion around at the moment."