(26-09-2016, 11:28 AM)michaelmcnulty Wrote: Guys,
Struggling to understand exactly what the question was after. I have managed to scribble down what is in the attachments but not sure if it was adequate or enough.
I ran out of steam in part D in terms of skills and roles, an area i need to brush up on...
Anyone kind enough to give some pointers on this one?
I've only had a quick look, but my comment is I think you need to think more widely.
Design could include design of the structure - is it on a gantry or post, mounted on OLE etc.
You could consider issues like reading through/reading across, also sun position (Phantom aspects), whether there are any signs and other distractions designed into the layout. Also you might mention that signal format complies with norms inc position of subsidiary aspects/indicator; indicator legends being obvious, and ensuring sighting of the indicator isn't worse than the proceed aspects.
Constraints can include access for maintenance (e.g. new signals on the end of Paddington platforms are folding LED type - they fold over the 4-foot which means a possession would be required). Also is there a place of safety for an SPT and if not is radio coverage reliable.
If sighting is poor (short) there may be banner signal(s) co-acting signals or approach control - the effects of which are added complexity, cost (to install/commission and maintain) and reduction in headway).
There are constraints at stations to ensure that trains don't stop half off the platform, similarly we don't want trains to stop foul of points i.e. to leave enough standage wherever a train may be stopped.
In electrified areas there are neutral zones and such like so if you stop the train there it can't re-start.
When looking at Signal positioning I think it needs not just the braking & aspect sequence but the stuff a Signal siting committee looks at. I think the last part is asking who should be on a Signal sighting committee.