It's a good idea for a thread, Tim. Clive and Stonehedge have said most of what needs to be said, so here's some overlapping input:
You help by taking control of the situation if you need to. If the person say they're OK when they're clearly injured or their bike is clearly damaged and they don't notice, insist on helping (or do it, anyway).
Try to gather as much info as you can, as per the list above. If in doubt whether someone else might be doing it, do it, too. It obviously depends on how much you want to, or can get involved.
Keep a duplicate of the info even if you hand it over to police, say.
You can also inform them that under the influence of an adrenaline rush, their judgement might be impaired, but like your friend they might not notice that if their judgement is too impaired.
I'm sure that many more tips will come, also based on personal experience of such incidents, and it would be good if you could edit the OP with what you think is useful to know.
It's a good idea for a thread, Tim. Clive and Stonehedge have said most of what needs to be said, so here's some overlapping input:
You help by taking control of the situation if you need to. If the person say they're OK when they're clearly injured or their bike is clearly damaged and they don't notice, insist on helping (or do it, anyway).
Try to gather as much info as you can, as per the list above. If in doubt whether someone else might be doing it, do it, too. It obviously depends on how much you want to, or can get involved.
Keep a duplicate of the info even if you hand it over to police, say.
You can also inform them that under the influence of an adrenaline rush, their judgement might be impaired, but like your friend they might not notice that if their judgement is too impaired.
I'm sure that many more tips will come, also based on personal experience of such incidents, and it would be good if you could edit the OP with what you think is useful to know.