These are my experiences of the wonder of disabled parking bays!
My parents are both disabled and when I was in my early 20's I was at the supermarket with them. They had parked in the disabled bays and after putting all the shopping in the car, I (being fairly healthy at that time) returned the trolley to the supermarket. When walking back to the car, I was almost run over by a man trying to park in the disabled space next to them before anyone else got it. His bumper actually banged into my knee, and when he got out of the car, no apology, in fact he began shouting at me for crossing over the bay! Anyways, Police were called etc etc and it was dealt with.
The next experience has happened to me a number of times. I was born with a deformed hip, pelvis and spine which I coped with very well until I was in my early 20's and had to start using sticks. I started having to use a wheelchair when I was 25 and was confined to it from the age of 28. Now without getting out the measuring tape and measuring my legs and finding a 2 and half inch difference in length, I look completely normal and I think this is where I have run into problems. For some reason, other disabled people, who are with no disrespect intended, in their elder years, seem to not realise that there are young disabled people out there. I have had abuse shouted at me and people accost me in my car when parking in a disabled bay about not having any right to be using them. Only when I have shown them my picture on the Blue Badge (or the old Orange ones) or my wheelchair and sticks in the car, have they begrudgingly backed off. Not once have I been given an apology.
No-one can look at a person and tell their medical history, not even doctors can. And there seems to be a part of society does not realise young people can be disabled too. Sometimes I have felt that I should wear a sign or have a clipboard of my medical records attached to my head!