dfreer Wrote:Does anyone know how to deal with turn outs when calculating stopping headways? If you have a branch off a main line (100km/h to 80km/h) via a 40km/h turn out do you have to include the 40km/h turn out in your calcs and the associated acceleartion / deceleration involved or do you just take the 'simple case' of the branch line speed and take it from there?
I'm looking at the 2002 examination layout 1 and (hopefully) am making things needlessly complicated.
Any help gratefully received.
To calculate headway accurately does require the calculations to reflect the speed profile that the train really adopts. Hence it should be obvious that if a train has to respect a speed restiction anywhere (and this includes the length of a turnout) that this should be factored into the sums and of course the decelration to that speed and reacceleration afterwards.
Indeed if the branch speed is less that that of the mainline (by greater than 10mph) then the junction signal would almost certainly be approach released (assuming UK mainline 3 or 4 aspect MAS practice). Hence the train speed on the approach to the junction would be constrained by the driver seeing restrictive aspects and your calculations would need to model that.
So in principle the answer is yes, absolutely definitely. However are you sure that the stated headway requirement applies to the branch?
In the example quoted the branch is only a single track line with no passenger passing loop but only an intermediate freight facility so the speed over turnouts is hardly the determining factor for "headway" is it? STOP TO THINK, don't just tap in numbers into a calculator determined by a formula.
READ THE NOTES: Contracted paths A to F, one passenger train per hour by day and by night 2 freight trains to the intermediate freigh facility.
It even says Required Headway for Mainlines.......
regards,
PJW