(31-08-2010, 10:14 AM)Varalakshmi P Wrote: Hi PJW,
Can you please tell me about TWO REDS RULE? On which condition and how we will apply this rule?
Thanks & regards
Varalakshmi Penneru
I am afraid this is quite complicated and you may regret having asked. It really needs some diagrams that I have not time just now to draw, but here goes a text explanation.
Double Reds
Relatively (>last 10 years) new thing to NR.
Basically in the past NR never had any train protection, then after some accidents fitted TPWS. Although not a 100% safety system, for the first time TPWS provision gives some form of certainty of how far a train could go if it SPADed.
At the retrofit programme, TPWS consisted of:
a) a TSS at the signal and,
b) where necessary, an OSS as a speed trap on the approach to the signal that would intervene if it was clear that the train going too fast to be able to stop at the signal (i.e. it acts upon anticipation that a SPAD will be inevitable).
Broadly (depending upon the type of rolling stock vehicles and the actual length of overlap gradient etc that exists) then this concept basically works ok for a passenger train running at up to about 60-70mph.
TPWS was conceived as a
PJW