And, for the practically minded, while rail and plane both can be closed down by incidents at the terminal, the entire rail line can be stopped by blockages from mechanical breakdowns, accidents and hoaxes. Where a flight might be delayed or cancelled, passengers can take a later flight or use an alternative carrier. Australia has enough white elephants, such as the Darwin to Alice Springs rail. High-speed rail is another we should not feed. Dr Gary Johns is associate professor at the Public Policy Institute, Australian Catholic University. The Economist: Saul Eslake FOR at least two decades the conventional wisdom has held that Australia's main population centres were too small and too far apart for a high-speed rail system to be viable. And that is probably still the case. But the economics of high-speed rail relative to other modes of transport are likely to change over the next decade or two, in ways that ought to prompt state and federal government policymakers to give serious thought to the role high-speed rail might play over the same time horizon that informs the government's Intergenerational Reports.

First, the cost of congestion of our road networks is high and rising. Last year's State of Australian Cities report cited estimates from the former Bureau of Infrastructure, Transport and Regional Economics that the avoidable cost of congestion in Australian capitals would rise from $9.4 billion in 2005 to $20.4 billion by 2020. This increase could be moderated by getting at least some inter-capital people and freight movements off the roads. Second, the competitiveness of high-speed rail relative to air travel is likely to increase. The rising cost of jet fuel, the increasing congestion and resulting delays at airports, the increasing amounts of time wasted by airport security rituals, and the inability to use laptop computers and hand-held electronic devices for much of the time spent on aircraft all heighten the potential attractiveness of high-speed train travel as an alternative to flying between the cities on Australia's eastern seaboard. Third, the drive to reduce carbon emissions is likely to increase the attractiveness and, depending on how we price carbon and our ability to generate ''clean'' electricity, the economics of high-speed rail relative to air travel and long-distance road transport. Finally, emerging trends in high-speed rail technology in Europe are beginning to undermine the conventional wisdom that has informed this debate in Australia over the past two decades. For example, the Spanish AVE system now runs from Barcelona via Madrid to Seville, a distance of just over 900 kilometres, compared with just over 700 kilometres from Melbourne via Canberra to Sydney, and serving cities with a similar combined population of about 8 million. The economics of high-speed rail don't stack up right now. But there's an increasing probability they will within the next 20 years. It would be foolish to wait until then to begin investigating the possibilities.

Saul Eslake is a program director with the Grattan Institute and adviser to PricewaterhouseCoopers.

OF COURSE not. Is the rest of the world so wrong in adopting high-speed rail as the future of their transport? The visionary leaders of China and the rest of Asia are building high-speed rail between their far-flung cities at an unprecedented rate, and even the car-obsessed, aviation-centric United States has adopted (and, more importantly, funded) high-speed rail as its preferred transport solution for the future. Australia is in grave danger of being left behind as we procrastinate with the politics and economics of the issue.

The clear message is the need to awaken and cement political commitment to the idea in Australia. Various examples from around the world have shown how the vision and determination of a single political figure can transform the landscape of our cities and regions for generations to come. With inspiration, leadership and drive, great change is possible. Yet, let us not forget that political will in isolation, will not suffice. Co-ordination, co-operation and integrative policies, led by industry and strong local authorities with the necessary powers, are also essential for any vision to flourish. But how to push high-speed rail up the political agenda in difficult financial times? It spills well beyond the boundaries of just ''transport'', especially in these times of unprecedented urbanisation. It has a rightful place at the core of our cities and regions as an environmental solution, economic enabler, social includer and major employer - powerful arguments are at the forefront. The undeniable qualitative arguments about the benefits of high-speed rail are well known. Improvements are needed to properly evaluate the variety of impacts of high-speed rail - notably, quality of life from a better environment and the effect on wider society from positive macro-economic effects. The need to justify the proper amount of taxpayers' money to be spent on high-speed rail requires decision-making based upon a better understanding of the benefits - but above all visionary leadership. In the past 100 years the world population has increased by a factor of four, carbon dioxide emissions by 17 and the production of goods by 40. As a nation, we face unprecedented challenges for the future movement of people and things. Traditional solutions will no longer cut it in the future. If we are really serious about having a go as a nation, do we really see our current transport networks meeting these challenges 30 years from now? Surely the role of our leaders is to test the envelope.

Peter Moore is Australia-New Zealand executive director of UITP, the International Association of Public Transport. The Director: Stephen Byron AUSTRALIA is too big not to invest in a high-speed rail network as part of the infrastructure development needed to accommodate our projected population growth and our future transport infrastructure needs. Our population is expected to grow from 22 million to 35 million by mid-century. Most of that growth will be on the eastern seaboard, yet Australia's three largest cities and its capital - Sydney, Melbourne, Brisbane and Canberra - are connected by what can only be described as an antiquated passenger and freight rail system. Our transport infrastructure is under strain and while the air transport options between these cities are world class, they need the support of high-speed rail to ensure the long-term provision of high-quality transport links. Consider this: The Sydney-to-Melbourne route is the fourth-busiest air corridor in the world - if there was ever a corridor that could support a high-speed rail network it is this one.

We are lagging other developed nations in the construction and utilisation of high-speed rail - China and the US are investing billions in the development of such rail networks. Both countries are geographically larger than Australia and yet believe that such high-speed rail networks are viable - why do we think such a network won't work here? Even if a site is selected for a second Sydney Airport, it will be remote from Sydney and a high-speed rail network will be needed to connect that airport to the CBD. Why spend billions of dollars on a new airport, and then spend billions of dollars on a rail network connecting the airport to Sydney, when for less cost ( financially and politically) you could link Newcastle-Sydney-Canberra with high-speed rail, facilitate the increased role of Canberra and Newcastle airports in providing airport capacity for Sydney, and create an economic corridor down the east of NSW? Loading This would also ease the use of roads and create a transport and economic corridor for eastern NSW: an area of industry, population growth, commercial development, innovation and further infrastructure investment. And it would be a corridor in which Sydney, Wollongong and the southern highlands could grow and which has none of the natural geographic and access problems that arise to the north of Sydney.

Stephen Byron is the managing director of Canberra Airport.