><<<<Speed proving has been existence in Sydney since the Underground was
>built in the 1920's.>>>>>
>
>Really?, the earliest reference I can find about speed proving by the society
>of British Signal Engineers, (where Australia got all of its signalling
>practices) is mid '50's.
Absolutely really truly conclusively indubitably (and any other similar adverbs).
Speed-proved signalling was an integral part of the design of the underground
because it was the fundamental method of providing the required capacity,
especially when you consider that the original underground had terminals at
St James and Wynyard, which therefore had added potential for blocking back.
One of the really distinctive features (at least in the second cycle of
installations in the early 1930's) was that a low speed signal could be displayed
at the entrance to a platform even though the train ahead was not yet actually
clear of the platform, PROVIDED that the track circuits had detected that the train
was moving quickly enough that it could not come to a stand in the platform even
if a full emergency application was made.
I only once ever saw this feature functioning, and I believe that it has now been
disabled. However all the other speed-proving features are still integral to the
system.
Eddie Oliver