The more or less current (week 4 and or week 5) TC have a couple of items about track circuit changes prior to S stock running.
One of the items refers to ''Tollerton'' circuits of 4.5 sec timed duration in place of Delta tracks.
What is this term ''Tollerton'' ? Is this a term for something all new, something that is not new but perhaps uncommon, or is this simply a name for the existing 4.5 sec timed tracks and just I've never seen the name before.
I see the TC also use the term ''Bubble car'' to refer to Chiltern class 121 single cars in the item about short trains potential problems. I was wondering therefore if ''Tollerton'' is equally as informal as ''bubble car'' is.
((I have a double interest in this one - if this has anything to do with ECML Tollerton north of York then thats one of the power signal boxes I visited in the past.))
'Tollerton Control' is defined by Network Rail as : "A timing delay incorporated into the operation of Track Circuits where there is a transition between SSI and RRI track circuited areas, and an incorrect track sequence of circuit clearance could give rise to a hazardous locking release."
In this case it relates to a short train passing from a conventional track circuit (with a very fast response - typically 0.3 sec) to a Jointless Track Circuit (JTC), which has a response time of up to 1.5 sec where there is a possibility that a short train could cause theconventional track circuit to re-energise before the JTC has de-energised, and the train becoming 'invisible' to the signalling.
I assume the 'Tollerton' name comes from the place where the problem was first discovered.
And that TC entry is appallingly written and shows how inflexible the immunisation works are!
WOW thanks Tom that was a quick reply I thought I might have been asking about the very obscure there.
I'll look into the NR stuff now, google failed to answer me with Tollerton and various other key words but now I now more detail I'll revisit it.
Agreed on TC wording - in general as well as in this case - some of it is not that good. Mind you, having re-read my post I see I confused 2 TC items, that of the Deltas with that of the Tollertons. I was doing this from home with no TC in front of me.