In message , at 12:28:33 on Mon, 21
Dec 2015, Clive D. W. Feather remarked:

Ely ------------------------------------ Peterborough
\
Ely ---------a-------------------------- Peterborough
\
*
\
b------c--------------- Kings Lynn
\ \
\ -------------- Kings Lynn
\
d------------------ Norwich
\
----------------- Norwich

Actually, a+c is a single lead junction, as is a+d. b is just a single
track junction.

A "single lead" junction consists of a crossover between the two main
tracks, a turnout from one track to the branch, and points merging the
two tracks of the branch.

OK, I wasn't aware if that subtlety.

As is fairly obvious, places like "*" are a monster bottleneck.

Actually, even worse is when the points just to the left of "a" fail in
the diagonal, rather than the straight position. (I've not seen it
happen in real life, but I have in simulation.)

It'd be worse if "a" failed towards Peterborough, wouldn't it?
--
Roland Perry