Business travellers relish the prospect of a new high-speed railway linking London and Scotland. But its success depends on pricing

Take a business trip from London to Paris or Brussels and it is highly likely that you will travel by Eurostar. In its 15 years of operation, the UK's only high-speed rail operator has come to dominate these two key business routes. As a result, airlines have cut or scrapped their own services in the face of the opposition. The line from London to the coast is known as High Speed 1.

We now have the promise of High Speed 2, a new railway line linking London and the West Midlands and possibly Scotland, designed to complement the existing West Coast main line, which is expected to be full to bursting by 2025 at the latest on current projections.

As the Eurostar case shows, high-speed rail is a viable alternative to short-haul flights and typically triumphs on journeys of less than around three to four hours. The body charged with looking at new domestic high-speed rail options is HS2, set up by the Department for Transport in March and chaired by the DfT's former permanent secretary, Sir David Rowlands.

HS2 is examining route and station options, the business case for a new line as well as its environmental and social impact. It will submit a report to the DfT by the end of the year. One possible option mooted is an international interchange station connecting the new line to both Heathrow and Crossrail.

Business travellers like rail travel. Its popularity has been growing substantially in recent years, according to business travel agencies. Part of the appeal is the ability to work at your seat and the increasing security hassles of air travel.

Much of the impetus for new high-speed rail lines comes from key environmental considerations. The UK has set an ambitious target of cutting its CO2 emission levels by 80 per cent on 1990 levels by 2050 and sees a switch from air to rail as a way of achieving this.

Transport secretary Lord Adonis says: "For reasons of carbon reduction and wider environmental benefits, it is manifestly in the public interest that we systematically replace short-haul aviation with high-speed rail."

Yet this assumes that rail is greener than air travel; this is not necessarily the case. In 2007, the DfT asked consultants Booz Allen Hamilton to look at the carbon impact of a new line between London and Scotland. It found that carbon dioxide emissions for a high-speed link, including its construction, was broadly comparable to air travel over a 60-year lifespan.

As with everything else, high-speed rail's domestic success will come down to price. High-speed rail fares will have to be competitive with the conventional rail and air alternatives. If they are not, Britain could end up with a high-speed white elephant.