David49
Whereas I agree that some 15 yr olds are streetwise enough to travel without coming to harm, there are a great many who are not, that is not only children either. Time and again you hear of attacks, injury of some kind or death because the individual is taking a risk that most would not.
But there are 20 year olds who are not streetwise enough to travel alone.
I think one must assume that if parents are letting a 15 year old, (and KA's son was within weeks of his 16th birthday) make a journey like this, then that child is likely have been being making shorter journeys and travelling around on his own for some years in the build up to the interrail holiday. The kind of paarent who wraps their child in cottonwool doesn't let that child interrail at 15.
One must also assume that someone like KA knows their son and is confident they can manage in an emergency. With my own children, one from a very early age showed themselves to be calm and quick thinking in any emergency, where the other tended to panic in those same situations, and that governed my own response to letting them do things on their own.