Catenary
Active Member
Ah, okay - it might have been the third-rail power supply I was seeing (lots of snow and wasn't really looking at the rails - I was looking up!). I seem to recall reading at some point they can physically move one of the rails to "regauge" the whole test track.
It's Page 7 of this PDF here:
http://www.bombardier.com/content/d...ston_Testing_Services_Brochure_2014_05_V1.pdf