I'm willing to bet it's a combination of things, car changing lanes maybe a little too quickly (or maybe not), and as usual....a biker gunning it to scoot past the car he sees changing lanes. I lost count of how many bikers see my blinker on, with me more than 3/4's of the way into the other lane, then they punch it to fly by the shrinking lane at Mach 1 speeds.....Suicidal! Here's a hint to bikers, don't pass a car on the side with the blinker on, and If you choose/must pass? Pass on the side without the blinker....DUH!