2009 Main Line Layout

[PJW]

If 3 aspect signalling is used for mixed traffic in the 2009 module 2 case, the distance from caution to red would be 2x the minimum figure for freight trains. Is this OK?
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Or to say it another way, does having an excessive distance between a caution and a red breed train handling complacency?

I guess in summary, can you confirm Reuben's assumption is valid? If so, is it a safety issue and/or a headway issue or something else?

To add to Peter's statement given above, there is inevitably overbraking for any trains running (because of their maximum permitted speed, their timetable, their attainable having joined a line from another of lower speed / after a station stop etc) at less than the speed at which the line is signalled (excepting where the reason why those trains are to run slower is due to their less good braking). We can't do anything about this and anyway we claim that driver's comprehend. What we are seeking to achieve is the complacency that can arise if they habitually find that vastly excessive distances exist between the caution signal and the red, so that they get accustomed to slowing only is step 1 braking for example; this leads to a trap when there is a signal section that really does need step 3 braking because of its short length. Actually there is an argument that CONSISTENCY along a route is just as important as the actual degree of overbraking.

I note that the exam question says to define all routes, however, Reuben's solution only includes route boxes for junction signals. Is this because not all routes need defining, or because of a UK practice I'm not aware of, or because the other routes are simple and so have been omitted to save time?

In most cases it should be immediately obvious to anyone where a signal with one route reads to; however where there is any ambiguity then there is a need to define- that could be where the track layout would actually permit more routes than the signalling system makes use of.
Where there is a junction then a route box is neede to define what, if any, approach release is envisaged, what route indicator is to be shown etc. As Peter says there are also instances when there is something "special"- perhaps it could be needing a slot from a shunter into a depot etc- and a relevant note is needed, so a route box can be a good way of showing.
In reality you are unlikely to have the time to do all that ideally you should- concentrate on the most important, which may mean only doing one of a group of parallel related signals so that you can devote your time elsewhere to give the best overall coverage. Don't waste time on simple ones that add little.

Also, please confirm, we don't need to show train protection for Main Line layouts, assuming the question doesn't ask for this. I only ask because Reuben's drawing shows some effort applied to include train protection, plus you mention previously a general AWS/TPWS note should be applied (as well as a specific note about the buffer stop and fixed red). Will this attract any marks, since the question doesn't explicitly ask for this?

Again it is a question of where to spend your time for maximum benefit. Certainly I wouldn't show the detail which Reuben has for the IRSE exam. However don't ignore train protection completely, so coverage by a detailed note s what I'd recommend, plus perhaps showing a typical associated with that note or there is a particular relevance (perhaps on a barely signalled single line branch).

Look at the module 3 layouts provided for Control tables as a good guide to what the examiners expect re detail on a module 2 layout.

Actually I think that the low prioritisation of train protections is one area in which the IRSE Exam has not kept pace with the UK rail industry- it basically reflects the pre-1990s view, which is significantly at variance to current practice in which we justify the overlaps provided partly on the basis of the effectiveness of train protection, so leaves me uncomfortable not to include at all. I guess that is why Reuben when producing a model layout to learn from (rather than on for production in the exam) shows as much as he does. Time constraints exist in the exam though and hence that is why I feel that stating a detailed assumption is the best way to address.

This comment applies to MAINLINE layouts; for METRO train protection is far more important (actually arguably more important as signals than the lights on sticks, where provided).