Exercise 1A, Appendix W of the Study Pack

[PJW]

I have included my calcs for question 1 below I have a query is the maximum permitted spacing for 3 aspect SBD + 33%?

Convert Line Speed into ms-1: 80 x (1609/3600) = 35.75ms-1
say 36ms-1

Find Braking Distance using the following formula BD = u2/2b, where b is the deceleration rate (usually given in the notes, assume 0.5ms-2 if not stated), and u is the train speed.

BD= (36)2 / (2 x 0.72) = 1296 / 1.44
BD = 900m

Maximum permitted spacing is SBD + 33%

SBD = 1258m + 33% = 1673 m

Sighting distance is 12 sec at headway speed = 12 x 36 = 432 m

Overlap = 180 m

Hd3 = (2B + S + O + L)

Hd3 = ( (2 x 1673) + 432 + 180 + 100 )
Hd3 = 4058 m

Ht3 = Hd3/V
Ht3 = 4058/36= 113secs round up to 115secs

Answer:
Headway time for 3-aspects at maximum permitted spacing = 115 seconds


Also is it best to submit my answer to the appendix as a job lot or can I submit them in this thread as I o them one at a time?

From my perspective I still have design for the commissioning starting on 24/12/10 to sign off as CRE and there are a million and one things to do to try to stop the whole job going very pearshaped; therefore I shall not have time to look at until 2011 so I suggest that you do as a combined lot.

Yes 133% braking is a typical maximum spacing, although in some circumstances this can be exceeeded it is a suitable value to utilise in this context.