My son, 15 and Autistic, loves trains! We have RR Track a few blocks from the house and he can identify a train by the sound of the horn. That’s no ****! He knows the engines, BNSF, Amtrak, and so on. He’s got 2 HO scale tracks set up in his room and can run those things all day and be a happy camper.
My wife and I, on a regular basis, get him more track, engines, freight cars, box cars, controllers etc. and he will write a list, a page full, of what he wants with the correct numbers. I’m amazed that he can/does have an YUGE interest in HO Scale trains. Hell, he even has a replica steam engine that he will run once in awhile.