Comment Re:Not another one... (Score 1) 120
Possibly the tunnels, besides being narrower in width, have curves in them, and the carriages were too long to actually turn [safely] within the tunnels.
The solution was likely to switch to more, shorter carriages - or even taper the front and rear of the carriages. However it might have been that the tunnel was still too narrow and would affect the max speed of the train.
In the UK they have rebored tunnels that are too small for modern trains. https://www.railtechnologymaga...