Boltar wrote:
On 29 Apr, 16:25, Steve Fitzgerald ] wrote:
St. Mary's Curve is indeed double track but due to the sharp curves,
the signalling has been modified to only allow one train in the
section at any one time due to the possibility of trains touching
each other.

That begs the question of why did they build the tunnel that bit too
narrow?

Or the stock that bit too big?

Seriously, though, 'A' stock was not around when the curve was built. The
length of modern cars and the distance between the bogies means that the
centre of the vehicles swing further out when curving than earlier short
wheelbase stock would have done, with the resulting danger of scraping
trains passing in the other direction. 'A' stock was never intended for the
ELL and only really ended up there as a result of their being some
flexibility in the fleet during a recessional period.