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2000 Headway calculations (stopping)
#1
Question 
So last week the London study group met to consider the tackling of the stopping headway calculations for the 2000 layout.  Note that our work assumed that we had already completed and were following on from the previous non-stopping calculation work (see previous thread).

At the session we basically worked through page 229 of the Module 2 Examination Resource Pack, issued 19/02/2008.  Note that the relevant reading is on pages 225-230.  I


Attached Files
.doc   2000 Headway Calculations Stopping.doc (Size: 32.5 KB / Downloads: 352)
.pdf   2000 Headway Calculations Stopping.pdf (Size: 145.88 KB / Downloads: 4)
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#2
In brief certainly must use the actual timetabled speed for headway, not the max permissible which is only relevant to braking.
Not readily in position to look at attachment and since this internet session costing more than a day's wages in this part of the world, I respond more fully next week! However I think it is quite probably that would achieve with 4 aspects reasonably widely spaced; certainly including approach released signals would do nothing to improve headway!

PJW

[quote=Douglas]
So last week the London study group met to consider the tackling of the stopping headway calculations for the 2000 layout. Note that our work assumed that we had already completed and were following on from the previous non-stopping calculation work (see previous thread).

At the session we basically worked through page 229 of the Module 2 Examination Resource Pack, issued 19/02/2008. Note that the relevant reading is on pages 225-230. I
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#3
(02-06-2008, 03:38 PM)PJW Wrote: I respond more fully next week!  
PJW
Douglas Wrote:Have I got this wrong, is my Newtonian Maths as rusty as an old piece of bull-headed-rail in a disused coastal siding?
D.

Sorry for rediculous delay in replying- I obviously overlooked this; it has only just come to light now others are attempting the same calculations.

The maths numbers were fine; however it was the signalling understanding that was a bit lacking and meant that you were probably setting out to answer slightly the wrong question.  Hence it was what you were doing routing your stopping passenger train into that disused coastal siding in the first place, rather than the rust on the rails that was the real problem.
Belatedly I have made amendments to your answer and attach here.

See the diagram "Fig 14" reproduced within section G18 of the Study pack.  However to make it cleare to people in future I intend (for 2011) to amend the text close to this diagram to:

The diagram below depicts such regularly spaced signals and the durations for which each of them displays restrictive aspects are drawn vertically.  The headway is the closest position at which the curve representing the front of the second train can be placed to that of the first, whilst still ensuring that Green (N.B. Double Yellow may be acceptable in the case of those on immediate approach to the station but ONLY where signals are spaced at minimum spacing: in such circumstances these restrictive aspects would make little practicable difference to how the train would be driven) aspects are achieved for the second train when at sighting distance prior to the relevant signal.

Suitable wording already exists earlier in the section but hopefully by expanding (and inevitably complicating) what was really intended as a summary should make it "more in face" when looking at the diagram.


Attached Files
.doc   2000 Headway Calculations Stopping DY with PJW comments.doc (Size: 52.5 KB / Downloads: 155)
.pdf   2000 Headway Calculations Stopping DY with PJW comments.pdf (Size: 160.07 KB / Downloads: 3)
PJW
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