Only significant changes in field limit size would have an effect, hence the 50 rider limit for Cat 5s.

That course isn't very helpful in promoting a safe race. I find the safest races are the extremely technical ones, the ones where you say, Omg no one's gonna make a lap before they crash! kind of course.

One year we raced in some residential area of Tarrytown NY. There was a short, steep downhill leading into a 90 degree right turn. There was a sewer grate on the left just before the turn in point. The grate was level so it acted like a ramp. You had to go over the grate else you'd be too far inside to make the turn (since you were flying down this steep hill on a narrow road). Everyone would hit the grate, get a bit of air, land hard, then jam on the brakes as soon as they landed. You had about a second of hard, hard braking, then you just dropped into the turn, leaned as hard as possible, and just cleared the curb on the turn out. You couldn't go slower because of the hill and the fact that you couldn't brake while you were in the air, so everyone has identical entry speeds, corner speeds, etc. After a lap or two of being petrified it was fun.

No crashes. Everyone had a great time, even just pack foddering. It was incredible fun blasting through that turn. I don't remember how I finished, I don't even remember the rest of the course. That corner was just plain fun.

Other races where I thought the course was close to impossible to ride around, no crashes.

Then you get wide open sweeping courses that are smooth and stuff and you get massive massive crashes because it's too easy, too wide, too smooth.