Expert reveals engineering secrets of railway

The spiralling viaduct near Brusio is one of the highlights on the Bernina line. Rhaetian Railway/Peter Donatsch

If the Bernina Express line wins Unesco recognition, it will become only the third railway in the world to be listed as a World Heritage Site. But what makes the line unique?

swissinfo spoke to Tom F Peters, author of works on historical building technology.

The Swiss-American expert, who is director of the Building and Architectural Technology Institute at Lehigh University in the United States, divides his time between the US and Poschiavo, which is located on the Bernina line.

Peters is leading efforts to organise special centenary events to mark the opening of the Bernina Express.

The line, with its stone viaducts and loops, was completed in 1910 and opened three years later, providing the people of the Poschiavo valley with their only year-round connection to the rest of Switzerland.

swissinfo: What is unique about the Bernina line?

Tom F Peters: The bridges are unique in the history of bridge building, because they were built a lot later than most full masonry bridges.

swissinfo: How much later?

T.P.: About 15-20 years than they ought to have been built. They were built for aesthetic reasons to bring tourists in to the Engadine, both from the north and to take them down south for a tour.

They are the only bridges built as full masonry bridges. That means there are no reinforcements – no reinforced concrete or steel. The only ones I found being built later than this were in Tibet and Nepal in the 1950s and 60s.

But as far as Western bridge building is concerned, these are unique in so far as they were built in strange configurations – on curves, on slopes – which really takes masonry construction to its utmost.

You really need tension members in them, to prevent sheer from occurring and bridges sliding and twisting and falling apart, and that was accomplished in pure masonry thanks to the engineers’ knowledge of static at the time, which was really quite advanced by the year 1900.

So they were able to build these bridges using an outdated technique, using outdated materials, for entirely aesthetic reasons.

swissinfo: As well as these attributes, you also say the Bernina line is one of the two or three steepest adhesion railways in the world. Why has it not already been listed as a heritage site?

T.P.: Since it is not yet 100 years old, it has essentially been considered a new line, but it’s slowly being thought of as historical. Now a decision has to be made. Either you do away with it altogether and replace it with something modern, or realise that you have something that is of aesthetic and technological value, above and beyond a normal railway, which it definitely is.

It’s also part of the culture of the two valleys, the Albula and the Poschiavo, since a lot of the locals were involved in building, maintaining and running it.

It has a completely different meaning within the development of tourism, within the development of the two valleys and their economy, their culture and their heritage.

swissinfo: Are historical railway lines, which are granted heritage status, more costly to maintain?

T.P.: They are expensive to maintain because the codes and guidelines governing the breadth of these bridges and what kind of escape routes you need if somebody is caught on the bridge when a train is coming, have changed so you have to adapt them.

And that needs a lot of careful design thinking. Very few engineers are trained in design in the sense of visual design and historical knowledge. There are a few here in Graubünden, particularly since these people are aware of their heritage, both in these bridges and other bridges.

swissinfo: The Rhaetian Railway was reluctant to put in a bid to have the Bernina line listed as a Unesco World Heritage Site. Was it worried about higher costs?

T.P.: The railway has to run at a profit. Maintenance of historical monuments is always more costly than tearing something down and putting up something new.

swissinfo-interview: Dale Bechtel

In brief

Tom F Peters is the author of “Transitions in Engineering: Guillaume Henri Dufour & the Early 19th Century Cable Suspension Bridges”, and “Building the Nineteenth Century”.

He is director of the Building and Architectural Technology Institute at Lehigh University in Pennsylvania.

Peters lives part of the year in Poschiavo.