What kind of a trail are you thinking of? Is it one specific trail or in general where pedestrians and using it as well?
30mph is really fast if it's a trail shared with pedestrians or a park recreational trail with dirt, tree branches and animals all over it.
If it's strictly a bicycle roadway where there's no chance of anything other than cyclists on it, then consider a head on collision with another cyclist travelling at 30mph means the both of you will collide at 60mph relative to each other. The mostly likely scenario would be if someone were passing a slow cyclist and is caught on the wrong side of the road.
Yesterday, I was involved in a bicycle collision. I was passing a jogger when another cyclist was trying to pass me at the same time. My regular pace was between ten and fifteen km/hr. Just as I was passing the jogger and headed back to the right side, I suddenly heard and felt the other cyclist's front wheel rub against my right calf and get caught against my peddle. She fell over but I kept in control and stopped. I told her not to pass someone who's in the process of passing someone.
It was all captured on my rear view camera. No damage, no injuries. We both apologized to each other and rode on.
Get a camera or two.