Well, my opinion is that the A group is generally safer, the tend to have better lines, and are much less of a risk then the I guys. The I group is the most dangerous group due to the following: Piss poor lines, You have people that just moved from Novice, You have people that should be in advanced, and less experienced riders sometimes freak when they get passed especially in a corner. Someone else with a piss poor line and who is inconsistent as they are cornering scares me more then being 2 ft off of someones tire in advanced or having someone pass me on the inside/outside from an A rider. The A riders can be trusted a bit more not to cut you off, not to change lines like a drunk, and not to target fixate on someone passing or while being passed. As long as you ride within your abilities and hold your lines, hopefully another rider will not do something stupid around you.. My guess is that if someone does do something stupid around you, it will be an Intermediate guy.