Wind in Gotthard tunnel slowing down trains
Greater wind resistance than expected is slowing down trains passing through the Gotthard Base Tunnel.
The first passenger trains are set to pass through on December 11 but the wind is threatening to play havoc with the timetable.
Instead of the planned 200km/h (125mph), air columns mean the train passing through the longest rail tunnel in the world will have a top speed of only 160-180km/h.
Out in the open the air flows created by every moving body can easily escape sideways or upwards.
But in the 57km (35.5-mile) Gotthard tunnel, there isn't much room as it was built almost 10% narrower than most tunnels.
The air columns must therefore be moved along both one-way tunnels by the trains – which requires a lot of energy.