In the not otherwise terribly pre-possessing railway sidings and yards around Basel Station in Switzerland, you can find some of the best signal boxes built in recent years. They are worthy successors to Birmingham New Street’s Brutalist signal box and in many ways resemble it, though I’m not sure the similarities between the two locations are as widely recognised as they should be. But this is the signal box re-imagined for the 1990s, doing away with bare concrete Brutalism in favour of an altogether more seductive and subtle exterior treatment.

The most famous of the trio is the Central Signal Box, which was completed in 1999. It was designed by Basel-based architecture practice Herzog & de Meuron.

Like New Street Signal box, it’s big and boxy, and its exterior is covered in corrugations. But instead of concrete, the corrugated effect is obtained by using 20cm-wide strips of copper cladding over the structure of the building underneath. The strips are twisted at various points to allow greater or lesser amounts of light into the signal box building. The signallers inside can see out through narrow horizontal rows of windows towards the top of the building, just as you can through the slats of a venetian blind if you stand close to it. But like a Venetian blind, if you’re on the outside of the building, it’s much more difficult to see in. Depending on the lighting conditions, it can be impossible to tell what’s behind the copper strips, or it might just be possible to make out the shape of the windows hidden behind, but you’ll have no luck seeing deeper into the building than that. Just a few rows of windows are left uncovered by the copper strips.

That sense of the hidden, the striving for anonymity even in a building which makes a substantial visual impact, is something else the Central Signal Box shares with the one at New Street. Like New Street signal box, it occupies an awkward site at the edge of the railway tracks, and is bounded on two sides by roads. The ground floor plan of the building is triangular, but as the signal box rises up through its six floors it transforms into a rectangular shape by the time it reaches the top. The copper strips disguise the stepping out of the underlying structure which achieves this, in favour of a smoothly twisting exterior, which presages the similar effect which would later be seen in Malmö’s Turning Torso tower.

With its location close to the street, Herzog & de Meuron was keen that the building should relate as much to the city of Basel as to the railway. According to the practice, the twisting building is intended to resemble, “something more organic and vulnerable, like a head or a brain, rather than a piece of technical equipment.”

The use of copper gives the signal box visual dynamism not just because moving around it gives ever-changing opportunities to peer through the copper strips to the structure underneath (or not), but because the copper itself reflects light differently depending on the weather conditions. On sunny days the signal box appears brightly copper coloured, flashing in the sunlight as the observer moves past, yet on cloudy days it can take on an almost grey colour with hints of dark brown. At night interior light from the building filters its way out through the copper strips.

Although the signal box is part of the urban fabric, rather than relating solely to the railway, that latter relationship is still at its heart. The Central Signal Box is a grander version of an earlier project, Signal Box Number 4, or Signal Box Auf dem Wolf as it also known. Signal Box Number 4 was completed in 1994, and pioneered the copper-strip cladding used on the Central Signal Box. But Signal Box Number 4 is a lot less photographed, sitting in the middle of the tracks of the rail yard to the east of Basel station. It has a much more conventional plan, and so lacks the turning appearance of the Central Signal Box.

The copper cladding was never intended to be purely decorative. It acts as a Faraday cage, ensuring that stray electrical currents pass around the outside of the building, rather than penetrating within, protecting the sensitive electronic signalling equipment inside. Those stray currents could come from lightning strikes, always a risk with tall buildings, or more commonly the passage of nearby electric trains.

Inside the signal boxes, there are no partitions within the workspaces, allowing maximum flexibility.

Herzog & de Meuron intended Signal Box Number 4 to set a standard template for new signal boxes which could be built throughout Switzerland, with the vision of a unified Swiss urban landscape. That goal hasn’t been achieved and Box Number 4 and the Central Signal Box present a unified design aesthetic but remain almost unique. Almost, because there is a third signal box, just to the west of Basel station, which also uses the copper exterior of the other two boxes. Completed at the same time as the Central Signal Box, this satellite signal box is much smaller. It uses copper panels rather than copper strips on its exterior, and this gives it a much smoother exterior. It’s even less photographed than Box Number 4. Herzog & de Meuron has a photo on its website, otherwise you can just see it peeking over the bushes in this Google Street View:

These copper-clad signal boxes might not have become the standard design in Switzerland, but they are a fascinating might-have-been and a landmark project for the railway in Basel. The Central Signal Box won the Royal Institute of British Architects’ Royal Gold Medal in 2007, and was mentioned in the citation for Herzog & de Meuron’s 2001 Pritzker Architecture Prize.

The next great step forward in railway signal box design would come when infrastructure authorities did away with signal boxes altogether and replaced them with something much, much bigger…

Bibliography and Further Reading

Herzog & de Meuron’s website is almost wilfully awkward in layout (which I kind of enjoy), but the project pages for the signal boxes can be found here (for the Central Signal Box), here (for Box Number 4) and here (for the Satellite Signal Box)

RIBA citation for Royal Gold Medal 2007, Central Signal Box, here

archdaily.com article on the Central Signal Box, here

mimoa.eu article on the Central Signal Box, which includes an interior photograph, here

How to find the Basel signal boxes

Click here for The Beauty of Transport‘s map