Any serious accident I think these days is investigated / measured etc in the same way as a open roads RTA i'm guessing for insurance, enquiry and coroner reasons, holding riders as mentioned by HH ^ is going to mean a loss of practice time / sessions. I'm all for safety etc but recently there are more reasons in place why a session is red flagged(apart from the worst outcome) but the potential amount of practice available does not seem to have moved on in a corresponding fashion. Another question that will need addressing is that if the incident is still being investigated when it gets dark which has happened how do you get bikes with no lights back safely ?