If it weren't a "serious" injury, maybe a broken bone or less, I'd say take a car, ambulance rides are ridiculously expensive and I'm guessing if they have to use it, that's going to raise the insurance rates for him which trickles down to everyone else. If your friend had a head injury though, that's whole different story.
As far as the 4/5 race, I did get out in front and try to push the pace a few times but no one would follow me. I don't have enough horsepower to solo to the victory on my own for a lap or two. I just wish there were more attacks, no one wanted to do anything so they just sat in and waited for the sprint. Anyway, lesson learned, I will be attacking more often and hopefully finding someone trustworthy to help out with the break.