Repeating Trek and Knotted:
If you fall, Pitch your helmet and buy a new one!
With the "Hard" shells on modern ones, it's had to tell if the helmet has recieved a fatal blow. Better to spend $100 on a new one than $100,000 on Hospital bills....
Knotted, not sure if anyone has told you this, but alway cross RR tracks at an 90 angle. Less chance of the tracks "grabbing" your wheel