How about a standard price per km, with some routes have a straight discount (to encourage use) applied in a transparent way? And additional discount fares available for specific trains of low use. And then apart from that, no travelcards, no discount for return fares, no break of journey allowed (because it would serve no purpose with flat fares), and the whole system (or at least that part that is practical) controlled on a touch-in touch-out basis? Also, all reservations to attract a small charge (to discourage speculative reservations) but to be available from an app and in realtime. Without a reservation, no 'entitlement' to get on a particular train.
That sounds like a guaranteed way to destroy the railways in the eyes of the travelling public.
Flat rates per km don't work when you have a network that includes both local and long journeys.
London to Manchester is about 200 miles, so let's say a single fare of £100 (slightly less than the current off-peak single). That gives you a "per mile" rate of 50p.
On that basis, Coryton to Whitchurch, at a distance of about 600m, would have a single fare of 20p.
If you set the fares at a level that gives sensible prices for long distance then local fares will cost more to collect than they will raise. If you set fares at a level that gives sensible prices for local journeys then long distance travel becomes unaffordable.
If you remove any kind of demand management (eg off-peak or advance purchase) then you end up with worse overcrowding at some times and emptier trains at others and overall a poorer usage of capacity and a less pleasant travelling environment. And no, people can't just "choose to avoid busy trains" as I've seen some people suggest, because absent any kind of price differential it may not be obvious to passengers
which trains are going to be busy.
If the payments are only managed by touch-in touch-out, how do you deal with the situation where there may be more than one route between two stations – are people automatically assumed to have taken the shortest route (even if it's very unlikely)? You would end up with all sorts of anomalies where it would be cheaper to travel further. (For example: Leeds to Goole is 32 miles on the direct once/twice-a-day train, so mostly you would go via Doncaster, which is about 47 miles. Which fare would you be charged? If you're only charged the cheapest, what about Leeds to Thorne North? That would be further than the direct Leeds to Goole route, so should be charged more, but is
en route to Goole for 90% of journeys.
"No break of journey allowed" seems like a very unfriendly way of saying "you can break your journey anywhere you like because it makes no difference to the fare" ... what do you even mean by "not allowed" in that context?
If fares are "all" controlled by touch-in touch-out, what happens when they aren't? Are you going to equip every station on the network with scanners (and barriers), and what happens if they are not working at an unmanned station?
Does it matter if they did? Only the odd enthusiast would ever do it, normal passengers wouldn't. I know the railway sometimes institutionally dislikes enthusiasts (despite having fares basically only ever bought by them like the All Line Rover) but it's such a small number of people that it's just inconsequential.
The main issue with this is because the mainline railway is a porous system (unlike say London Underground) people would "break their journey" at a distant station and pay less than they should pay. But for contactless you can't tap off somewhere you didn't get off the train so it's fine.
I remember 20 years ago when there was an anomaly in the Routeing Guide that meant a ticket from London Terminals to Finsbury Park was valid from Liverpool Street via Cambridge. Sure, that loophole has been ironed out, and was not widely known at the time outside train geek circles – but these days, with far more mainstream websites openly advertising split ticketing and other workarounds, you can expect any oddities like that to become much more quickly and widely exploited. And, as in the example above, there
will be absurd situations where distance-based fares give really counter-intuitive results.