I actually googled it after posting, disabled vs non disabled is one of very few things the law allows more favourable treatment for a group against the other.
And the reason for it is that what is required is equality of opportunity.
Disabled people are reserved parking spaces right in front of Tesco, I'm not. That's because if they weren't, they may well not have the opportunity to visit Tesco at all, as they wouldn't be able to walk far enough or a regular space might not be wide enough to get their wheelchair out of the car and transfer to it.
Similarly, if in a PF area a disabled person cannot use a TVM, perhaps because of being blind or nearly so, or because they can't bend over to reach the screen[1], if they are not allowed to pay on board (or allowed to travel for free, if the cost of collecting their fare exceeds the loss from not doing so), they are denied the ability to travel by train. Whereas I can use the TVM. Perhaps worse - I can also cycle and drive instead if I can't be bothered using a TVM, a blind person can do neither of those things.
So just as I don't begrudge the disabled parking space, or the disabled toilet, I don't begrudge that either.
[1] I think, with people getting taller, things put at wheelchair height only are a disability issue storing itself up for the future as my generation of 6-footers become less mobile and able to bend to that height. One advantage of the gimmicky "smart wall" ticket machines is that the large screen could put the regular-sized TVM display at the height of the user's choosing, and thus solve that issue.
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The thing is, again without intending to sound unduly harsh, a teenage girl out late is hardly the same as a disabled person. The girl has ended up in that situation through their actions (e.g. stayed out later than they are supposed to, or chosen to go somewhere they should not have) a disabled person has not. The teenage girl is only vulnerable because it is late at night, the disabled person is disabled 24 hours a day. Once the girl gets home she's no longer at risk, the disabled person will continue to be disabled.
And if she got out of a car she was presumably dropped off at the station by an adult, who has some level of responsibility for her by having done so. If they didn't wait to see that she was able to buy a ticket and board the train, they perhaps weren't discharging that properly.