Matthieu Lafaurie, director of communication for the LISEA consortium that includes VINCI, one of the world's largest construction companies, says studies show two hours is the key to unlocking economic development and boosting passenger numbers for both business and leisure. ''Two hours is the time where business travellers say, 'I can go from Paris to Bordeaux for a meeting in one day, it's not so complicated'. If it was three hours they would not go.'' In Australia, a study by AECOM consultants, commissioned by the former Labor government and released in April, found it would take until 2065 and cost $114 billion to build 1748 kilometres of rail linking Melbourne, Canberra, Sydney and Brisbane. The journey between Melbourne and Sydney - among the busiest flight paths in the world - would be cut from 11 hours by train to two hours and 44 minutes. Last month, research organisation Beyond Zero Emissions, working with German engineers, modelled a 1799-kilometre route using fewer tunnels and bridges for $84 billion.

Those in favour of high-speed rail cite the creation of thousands of jobs, reduced greenhouse emissions, less road traffic, improved access to regional centres and the ability to deliver passengers into the middle of capital cities. Opponents argue the cost is prohibitive and that unlike other countries with high-speed rail such as France, Germany and Japan, Australia's major population centres are too far apart for anything but air travel. Assuming competitive ticket prices for the estimated 19 million passenger trips each year between Sydney and Melbourne, the most recent government study calculated a rate of return of 1 per cent on public investment in high-speed rail. Dr Chris Hale, a lecturer at the department of infrastructure engineering at the University of Melbourne, believes the study was right to prioritise the Melbourne to Sydney route, which is estimated to cost almost $50 billion and take about 30 years. ''It is not $50 billion in one hit, it is broken down over 10 to 15 years and you break it down between the federal government, two or three state and territory governments and possibly local governments for certain things like stations,'' Hale says.

''When you start doing that it looks a whole lot more achievable, and a whole lot more realistic and sensible.'' The Tours-Bordeaux line, costing €7.8 billion ($12.07 billion), was financed under a public-private contract. The French authorities provided half the funds via €3 billion in subsidies (half of which came from local authorities) and a €1 billion contribution from the National Railway Network. The LISEA consortium put up the other half through bank loans (60 per cent of which were guaranteed by the state) and €1 billion from the European Investment Bank. Rather than receive a fixed fee, the consortium will recoup its costs through a concession over the line until 2061. It will be reimbursed by the state rail operator for each journey, effectively taking the risk of weaker-than-expected passenger numbers. The contract also includes a common clause in France requiring 10 per cent of those employed by the consortium to be drawn from the ranks of the long-term unemployed. About 8500 people are directly employed on the project and Vincent Hulin, an editor at local radio station France Bleu Poitou, says there have been flow-on benefits in a region with few staple industries.

''It is the indirect jobs as well,'' he says of the locals who provide essential fencing, security guards and cement. ''Opposite the consortium's headquarters there is a restaurant and 50 people eat lunch there every day.'' Benefits to towns along the route are largely limited to the construction phase as they swell with workers, some of whom choose to live in caravans on site. Congested roads and noise pollution have prompted some locals to stand outside theatrically checking their watches as the 10pm curfew approaches. High-speed rail in Australia is promoted as a boost for regional centres such as Shepparton, Albury-Wodonga and Wagga Wagga. To reduce cost and disruptions the government study recommends these stations be placed no more than 20 kilometres outside town and linked to local public transport. Hundreds of millions of euros were added to the Tours-Bordeaux project when the mayors of Poitiers and Angouleme insisted on 38 kilometres of extra track to connect their towns to the main line, rather than building stations along the new route. ''The politicians all want their trains to arrive in the middle of town, it's all very 19th century,'' says Pascal Roche, editor-in-chief of France Bleu Poitou. ''It's clear today that everyone is lying in this story. In 10 years the station won't be here. The [state-owned rail company] SNCF will say one day, 'No, for our trains to go quicker we will pass over there'.'' That is, near the airport on the outskirts of Poitiers.

Tours-Bordeaux is the biggest construction site in Europe and will be built in five years by dividing the 340 kilometres into 15 sections being worked on simultaneously. It will take two years to dig 68 million cubic metres of dirt and create 500 structures (including seven tunnels, 450 bridges and 24 viaducts), two years to lay 91,500 tonnes of steel rail, overhead wires and signalling, followed by one year of tests. For the final three months, trains will operate on a normal timetable without passengers. The line threatens the habitat of 220 endangered species: frogs, insects, birds, snakes, fish and bats. ''It is a complex ecosystem that we are disrupting,'' says Dumeaux, who is working with local conservation organisations. ''But I'm confident in our ability to avoid, reduce and compensate for our impact.'' New trees are replanted nearby to replace those cut down, and for every pond destroyed two more are created by transplanting flora and fauna from the initial site. Accidents such as occurred in Santiago de Compostela, Spain, in July - where 79 people died when a high-speed train took a corner too fast and derailed - will soon be impossible, says director of operations Stephane Brondino, thanks to an emergency shutdown system triggered if the train exceeds the mandated speed for too long.

Asked what advice he had for Australia, Brondino says ''the key is to define the route, a clever route: easy to build and maintain and with minimum disturbance of the neighbours''. Although building close to the highway may seem more logical this also adds costs and delays during construction. ''If instead of being 50 metres from the road we were 200 metres it would be several per cent cheaper in those areas,'' Brondino says. This month, shadow infrastructure and transport spokesman Anthony Albanese - who has met French high-speed rail operators - introduced a private member's bill to protect an east coast corridor from urban sprawl through the creation of an 11-member high-speed rail authority. A spokeswoman said the government was yet to consider the bill, though Infrastructure Minister and Deputy Prime Minister Warren Truss has written to the state and ACT governments to gauge their support for reserving a corridor.

Aside from the ''hideously expensive'' process of gaining access to capital cities with sound barriers and tunnels, Hale says Australians may be pleasantly surprised how amenable the landscape between Sydney and Melbourne is to high-speed rail. ''You are going to have some reasonably good, flat, open country, low levels of population. It has probably already been deforested for the most part in broad swathes of where the corridor will be.