2005 Module 2 Layout Calculations

[alexgoei]

Hello PJW,

Thanks. I understand your point about the contingency in deriving the technical headway being dependent on what the exam requires. Appreciate it.

I would also like to submit my calculations for the 2005 Layout which I hope you and other participants to this forum may wish to comment.

Thank you again and look forward to your reply.

Your presentation of the non-stopping headway is very concise and quite clearly presented.

For stopping, you have made an assumption that will not always be valid - ie that there is a starter signal near the end of the platform. In so doing, you have "saved" yourself some of the time that is wasted when the train is accelerating. If this was not the case and the train had to travel sufficiently far that it gets back to line speed, this part would be longer and the time at line speed slightly less, so you would find you are a bit nearer the mark (I think in this case you would be OK, but you have not proved this). Check that the numbers work if the station and the acceleration come just after the signal.

Your table presentation is good, but some of your headings are misleading. You have called section b "distance between signals" when in reality it is "distance between signals minus the distance it takes to decelerate".

Other than that, you seem to have done it well.

Peter

Hello Peter,

Some further points to clarify please:

1 In the IRSE Study Pack (the IRSE Support Materials), there is a power point presentation on Calculations. I noticed that when using the Train Length to compute the Non-Stopping Headway, the longer train length value was used even though the permitted speed value (in this case of the Freight Train) was slower. Should we therefore be always using the longer train length?

2 Your point about saving some time when the train is accelerating to reach full line speed - So would it correct to say that to determine if 3 aspect signalling could meet the stopping requirement headway of 218 secs (with 10% contingency) it would be necessary for completeness to incorporate a further 15 secs which is the time taken in order to reach the full line speed of 100 km/h? If the answer is yes, for this particular layout and with 10% contingency, the headway time between 2 trains both travelling at 100 km/h would be 226 secs. And therefore the conclusion that 3 aspect signalling would not have been able to meet the stopping headway requirements.

One more point to add for all taking the exams - in the 2009 paper the requirements are very clear - no contingency in the headway computation. Other students may wish to take read and take note of this should it appear in the exams.

Look forward to your reply

Cheers