The 1997 paper Routeing Guide had 27 maps. By 2011 the number of maps had increased to 125. The current version has 352 !
That may have something to do with it.
Another potential issue is that, back in 1996 there was a Routeing Guide, it was definitively
the Routeing Guide. The journey planners of today use 'their version' of the Routeing Guide, whilst the .pdf format Routeing Guide, which replaced the 1996 paper version, is also 'a version' of the Routeing Guide which contains 'written versions' of the easement codes that are pumped into the online journey planners to make them work as planned and thus can be confusing or just not make sense. All of this means there are multiple interpretations of something which relatively few people can actually see these days.... The Definitive Routing Guide....
....You put in your starting station and your destination station. The system works out the valid routing points and the combinations of maps you can use, taking into account fares and easements.
It then presents to you the list of map combinations you can use. You then select with combination you'd like to use, if a choice exists that is and then the maps with routing lines appear on your screen. So you wouldn't just be lookibg looking at each routing map in turn but multiple maps at once.....
I actually like that idea, maybe each map is a different colour so you know where one ends and another begins. This could possibly be done with each map being a 'layer image' over a map of Great Britain, meaning you'd only have to program the app to apply certain layers, rather than compose a new map for each journey. Of course, the biggest problem with this is 'Easements'.
....Each route would have to be colour coded and you'd have to be able to switch one off or no due to the possibility of overlaps according between maps...
I think it would be better to offer the various maps combinations to select before the map is shown. Less confusion that way I think.
....Perhaps they could even allow you to trace over the lines using your finger and then determine if your route is valid. That bit might be too complicated so the first idea would be better.
Perhaps someone could explain why my above ideas couldn't be implemented....
Updates, aside form easements, the biggest issue would be changes that ATOC want to make to it, be it the instructions, maps, routes, easements, whatever, every time that changes the app would have to be updated.
....My thinking is that there are two primary asks:
1) To establish whether a particular route is valid
2) To view all possible routes between two points....
The first already exists I think, at least in the form of online Journey Planners, the second is more tricky. Even London-Glasgow isn't exactly 'simple' with six possible starting stations in London.
....If there are a large number of variables and permutations, I would have thought that this would be performed far better by computer.
The computer has to be programmed by someone though, and then it has to be checked for accuracy, and, presumably, accredited by ATOC.
....[ The fares data you need to find appropriate routeing points is publically available too if you want to have a go.]....
The Journey Planners are supposed to take into account fares from April 96 (NFM64) which are not as widely available, though still possible to get.
The permitted routes don't only consist of mapped routes. You would also need to show all possible routes within 3 miles of the shortest route. This is particularly difficult to show, as although there may be multiple valid deviations possible at one stage of the journey, choosing one of these deviations may reduce the possible deviations allowed at a different stage of the journey (due to more or less of the 3 mile "flex" being used up).
On a forum that can't agree what 'the shortest route' actually means, that could be an issue.
Also, whilst direct trains are not strictly permitted routes, they are ways that a ticket can be used which may provide an alternative option.