The formula giving the MAXIMUM spacing is from the HEADWAY constraint.
You also need to satisfy the OVER-BRAKING constraint.
So it is not a question of which to respect; there are two constraints and you must satisfy BOTH. In any particular situation, you use the limiting factor- the one which is the SMALLER of the two MAXIMUMS.
If can't achieve whatever this MAXIMUM is plus the MINIMUM derived from BRAKING, then use 4 aspects instead.
This is the sort of question that can be answered from an iPad; today I am travelling to Stratford Olympic Park wearing a magenta-pink tabbard with a mission to get the hoards to use West Ham station instead!
I am conscious that I still owe other replies, but they need to wait until I have suitable iopportunity to respond, unless someone else takes up the reins!
You also need to satisfy the OVER-BRAKING constraint.
So it is not a question of which to respect; there are two constraints and you must satisfy BOTH. In any particular situation, you use the limiting factor- the one which is the SMALLER of the two MAXIMUMS.
If can't achieve whatever this MAXIMUM is plus the MINIMUM derived from BRAKING, then use 4 aspects instead.
This is the sort of question that can be answered from an iPad; today I am travelling to Stratford Olympic Park wearing a magenta-pink tabbard with a mission to get the hoards to use West Ham station instead!
I am conscious that I still owe other replies, but they need to wait until I have suitable iopportunity to respond, unless someone else takes up the reins!
(08-08-2012, 05:44 AM)NJK Wrote: Dear Members,
In 3 aspect signalling, the maximum signal spacing "d" is calculated by using following formula
d = ((Vh x Vt) - (Sd + O + L)) / 2
some times the calculated value "d" is exceeding the value 1.5BD. If the value d exceeding 1.5BD then risk assessment is required.
My doubt is whether I have to use 1.5BD or d for maximum signal spacing.
Kindly clarify.
Regards,
NJK
'
PJW