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+---- Thread: Headways (Stopping) calculations- info required (/showthread.php?tid=60)
Headways (Stopping) calculations- info required - PJW - 08-06-2008
rahul_bhasin wrote to me as an individual but is an item for wider audience:
Quote:Sir,
I need some notes/study material in connection with for Headways(Stopping). In IRSE exam which method we should adopt - Graphical or Mathematical?
The extract of the Module 2 Study Pack I placed on this site early in the year only contained the constant speed headway calculations but the completed version (March 08) did include what I think you need.
You should have been given this free when registereing for the IRSE Exam; if you haven't been sent this then please let me know as soon as possible since that is something which I would want to take up with the IRSE as a matter of urgency- there is no point in having taken the effort to produce something if it is not being made available to students. Perhaps however you are wishing to study now for an examination to be taken in 2009 rather than 2008 and so have not registered; this is an issue which I know has not yet been addressed by the IRSE. In this case I'd appreciate you raising directly with the IRSE (contact = Christine White) in order to apply some pressure to agree a resolution but in the meantime I could email you the relevant portion privately.
In brief you may use either method; indeed to me there is only one "method"- it is just whether the detail is all included in the drawing or is sub-contracted to separate calculations.
I'd personally tend to calculate but include a "not to scale" sketch to support the answer; this is because I'd know I'd have difficulty in exam conditions to determine approprate scale and draw sufficiently neatly to get accurate answer directly from the diagram. I also feel that graphical is probably more appropriate to the Metro approach (position signals to protect conflicts taking into account calculated overlaps and then add additional signals as necessary in order to deliver headway requirement- an iterative approach) rather than the UK Mainline approach (all signal positions relevant both for headway and for braking to a further signal at danger- thus need to form view about implications of the headway requirement initially before placing any signals at all).
Suggest you read the above and the Study Pack (let me know if not available to you) and also the material already posted by Douglas under a separate Module 2 thread; should things not be clear then please post a follow up.
Note that there is a "sub-forum" into which various attempted mod2 calculations have been placed- to see these posts click on either the lower case text "Calculations: Past Papers and Exercises" within the Module 2 area of the Main Page or in the top area of the screen you obtain when click on Module 2 from that page and get a listing of all the threads- this will reveal those in the sub-forum
PJW