Stopping Calcs - Turn Outs

[PJW]

Peter,

Would this mean a calculation is need for the initial section of line going into the first station, then a separate calculation for after the first station to account for the greater approach speed?

Neil

If you really have to assess the headway for a line then yes you have to do the lot to ensure that the required headway can be delivered. However remember that headway is determined by the WORST section. No way does it "average"; it is limited by the bottle neck. You don't need to calculate the headway that would be achieved by each particular short stretch of signaling in isolation; just that overall your solution delivers. Thus you need to spot what is likely to be the limiting section and prove that is OK.

Hence in this case I suggest you concentrate on the area around station D and if you have the same signal spacing relative to station G then you know that will be better. The issue is that other constraints (e.g. that level cossing- signal on the approach and also constraint re standage re the position that the one beyond it can sensibly be placed) may force you to increase signal spacing so may not be intuitive obvious that it will achieve. However in the exam you'll be too pushed for time to redo calcs- the stopping calcs are only about 10% marks so just can't afford to take any more than 9 minutes. Once you've shown you can do calcs it'll certainly be the law of diminishing returns- you are better investing your time elsewhere ........