I was in London the other day traveling on the Central Line heading West. On our journey we had to pass the closed station of Tottenham Court Road, and as we passed we were going, perhaps 15mph, through a fenced off platform area. Its the same for other closed stations I passed through in the past. Im just curious as to why the speed restriction. Is it a rule in the book, or a health and safety aspect for workers? Signalling? I figured it would be nice to just whizz through a closed station at line speed.