A few years ago perhaps no-one would have believed that it could ever be faster to cross Europe by rail rather than by air. But as rail connections improve, air travel is becoming less attractive.

A network of high-speed rail lines is springing up all over western Europe. Train travel has many advantages. Unlike airports, stations are normally in city centres. Travellers need not set aside extra time to get there; check-in is usually much faster than for planes. And trains are rarely held up or diverted as a result of bad weather.

It is in this context that the Swiss, inveterate tunnel builders, have embarked on the New Railway Link through the Alps, as it is officially called in English, also known by its German acronym, NEAT or as AlpTransit. At the heart of the project are two "base" tunnels, the Lötschberg, (34.6 km/21.5 miles) and the St Gotthard (57 km/35.5 miles). Because they go through the base of the mountain and do not need to climb, the line can be much straighter than in the current tunnels where they are forced into curves and switch backs in order to gain the height to reach the entrance. The Gotthard base tunnel, long as it is, will cut 40 km (25 miles) - from the total journey between Altdorf in canton Uri and Biasca in canton Ticino. The tunnels will link up with high-speed lines in Switzerland and beyond, ensuring that the country remains a key element in north-south traffic.

The project will cut travel time between major cities. Not only will it shorten the number of kilometres travelled, but it will be open to high-speed international trains, like the German ICE or French TGV, which cannot use the current tunnels because of the gradient. Passenger trains will travel through at 250 kph.

But improved international transit links are not the only benefit. The southern cantons of Ticino and Valais will be less isolated. When it only takes two and a half hours instead of four to get from St Gallen to Lugano via the Gotthard base tunnel, perhaps people will think of nipping over for a day trip... The Lötschberg base tunnel has chopped an hour off the Bern-Sion journey and opened up central Valais.

The project will also contribute to Switzerland's ongoing effort to ease congestion on the roads. The NEAT is expected to take 90% of the goods in transit through Switzerland. Because the line is almost flat, goods trains can be twice as heavy as those which have to climb to today's tunnels - 4,000 tonnes as against 2,000 tonnes - and they will go faster: 160 kph (99.5 mph). The number of goods trains passing through the Gotthard alone should increase from the 110-130 per day at present to 200-220, carrying 40 million tonnes of freight a year.

Construction methods

Tunnel construction is proceeding in several places at once, not only from each end, but also from intermediate points, reached by lateral tunnels. Both consist of two single track tunnels, about 40 m (130 ft) apart. Cross-over tunnels enable trains to move from one track to the other, for example when one tunnel is undergoing maintenance. The twin tunnels are linked with connecting galleries at regular and frequent intervals, which will provide escape and refuge in case of accidents, and the intermediate access tunnels, used as working points during the construction phase, will give access to rescue workers.

Both blasting and tunnel boring machines are used to build the tunnels, depending on the type of rock. The geological conditions vary considerably along the two routes. The most challenging stretch, near Sedrun, on the Gotthard, has been described as being like "toothpaste" and needs special tunnelling and support methods. In other places - for example in the southern part of the Lötschberg - geologists found rocks containing water under huge pressure (1,200 t per m2/111.5 t per square foot). For environmental reasons the amount of water they are allowed to remove is limited, so special cement was injected at high pressure into the rock in order to seal it. At great depths under the surface - in the base tunnels up to 2.5 km (1.5 miles) - the temperature can rise to 45 degrees (113 degrees Fahrenheit), making for unpleasant working conditions, and the difference in humidity between in and outside can be close to 100%.

Tunnelling ran into unexpected geological problems in both tunnels. Delays in the Lötschberg were not great: it came into use in June 2007, about a year later than originally hoped. The Gotthard, originally planned for 2012, will not come into use before 2016.

Future developments

hese two tunnels are not the end of the project: further tunnels are planned to improve the Alp transit line. Construction of the Ceneri base tunnel started in June 2006. It will run from Vigana, just south of Bellinzona, to Vezia, just north of Lugano, for a total of 15.4 km (9.6 miles). It is expected to open in 2019. However, the planned Zimmerberg base tunnel between Lake Zurich and Lake Zug designed to link Zurich with the new Gotthard tunnel has been put on hold.

Finance

And how is this ambitious project being financed? Most of the money for rail modernisation is coming from taxes of one kind or another. The biggest single source is the Heavy Vehicles Tax (paid by trucks for the right to cross Switzerland by road); some of the finance is coming from VAT, where 0.1 % of the receipts has been earmarked for the project, and an oil tax will be a third souce. The remainder comes from loans.

The costs are rising, not least because new safety measures are being introduced and some of the original plans have been altered. Some politicians see the project as a bottomless pit, and have called for some of the planned developments to be halted.