Bad crash - hit from behind

Keep in mind that you're referring to racing on a specific course where all competitors should be going in the same direction.

From the 2012 AMA rule book
The rider must be able to control his/her motorcycle at all times, and to ride it safely. This includes
stopping, starting, standing still, mounting, dismounting, and putting one or both feet on the
ground. The referee has the authority to disqualify a rider who can't safely control his/her motorcycle.

A racer who is riding one side of the course then suddenly darts to the left to pull off the course, causing a collision with another rider, would be considered an unsafe maneuver.

A blue flag does not necessarily indicate that a faster rider/car is passing from behind. While there are some slight deviations of the description of how a blue flag is addressed, they are basically similar.
As AMA puts it:
BLUE: Indicates you are about to be overtaken by faster riders. Hold your line and don't impede their progress.

Some rulebooks basically describe the blue flag as the slower racer must get out of the way as soon as possible because of a faster racer. And if the blue-flagged racer doesn't move damn soon he's black-flagged.

As the former competition manager of an international motorsports sanctioning body who also had the role of race director at national level competions, I have a little experience in this area.

Basically the OP was not in an organized competition, and therefore those kinds of rules do not apply.
The best rules that apply here are common sense, and that is don't make a left hook turn across the trail without looking.

 

Good points 2wheel_lee. But in my opinion, on recrational rides the overtaking rider has the responsibility to pass responsibly and be under control at all times. You never know what the guy in front of you is doing, and each one can chose different routes, or have to make a sudden move to avoid whatever. I always keep a safe distance from the guy ahed or pass on a flat or climb.

The incident happened where there is a legal single track on the left, rider from behind was probably at 30mph passing between me and the trail entrance without a warning.

 

Did you read my entire post, including the last paragraph?

 

It doesn't really make sense to pass someone (who's intentions you don't know) at a trail juncture. Just feather the brakes and time it so you're passing in an area where there won't be any confusion.

 

It kinda sucks when someone pulls a "Crazy Ivan" in front of you. I thought that move was reserved for submarine hunting and snow skiing or boarding. Sorry to hear about the injury, but the sudden left turn from the far right leads to problems. It would have been nice if the guy hit a trail bell to let you know he was coming up or as you mentioned an "on your left" 50/50 imho

 

Nothing is ever cut and dry with accidents. However, there are some simple rules.

You get hit from behind, he's at fault.

Why is that, because he sees you. You may not see him.

He makes the conscious decision to change the status quo and overtake you, initiating the action that cause the accident.

It is his fault. Left hook turn or not.

There is no arguing that. Otherwise, determining fault ends up being a he said she said affair, which doesnt solve anything.

You get hit from behind, the other guy is at fault. On the street, or not. Unless, ofcourse, you were backing up

Announce your presence and intention when overtaking. It's common sense.