I did have a quick look on the RSSB website but couldn't find what I was looking for so anecdotally (with a smidge of real experience and industry knowledge) There are various ways of dealing with incidents. One strategy is to keep your diagrams sufficiently varied to prevent under-load or risks introduced through constant repetition. This is particularly relevant for Metro routes where you can run over the same route multiple times in a day. This can lead to assuming where you get signalled and predicting signal sequences. This can also apply to mainline routes, especially where routes may be epic in terms of mileage but not in variety.
Another reason for varying routes on a diagram is to help with route and traction knowledge retention. We have routes where they are limited by traction. We have diagrams that are used purely to maintain route knowledge. The whole Driver diagramming can be incredibly complex. There may be a case where trips do not fit is an diagram so need to be split. I remember an issue with a Thameslink depot where they discovered that you could drive a route in one direction but wouldn't be able to make it back to your depot in the same diagram; so it gets chopped up into chunks.
I'm not saying that this is specific for Avanti but I can understand why it may occur.
This opens up too many questions for me. 10 days a year is a tiny amount in real terms. I've refresh many routes in my years and some will take a day to get and in some cases, just a single trip. I'd also ask if the routes that need to be covered run regularly. We have a few routes where trains rarely run so trying to get that refreshed can be a miracle at times. When you limit route refresh days, you are also reducing the opportunity to get them. This introduces the risk where Drivers could simply remove the route from their route cards which would cause more issues.
I'd also want to know what the route learning strategy is. Does each route have a minimum number of days required to maintain competence ? Are the routes covered by a suitable route story with different learning styles incorporated to any learning plans ? Can they be learned digitally etc. ?
I'd also ask about how the refresher days are used. Are they booked on the roster and used as spare/as required turns or are they specifically restricted to route refreshing as
@LowLevel level stated, you often get pulled off your refresher days for other duties. By having multiple days in the roster booked for routes gives you the flexibility and helps reduce costs with providing refresher days that would require rest day working.
My depot doesn't have specific route refresher days built in because the theory is that they are easily missed. I could be on leave that week, on a course, assessment, off sick, etc. Again, its about giving you rostering flexibility.
I don't work for Avanti so its difficult to comment on their depot specifics but there are always underlying reasons for some of the oddities of the weird and wonderful place we work.
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I said yes last time and ended up working 1515 to 0100 for my pains!
