I Feel most vunerable in large lines of traffic or around tall vehicles where people can't see you.

The only times I've had problems is:
1.) a professional driver (and I'm using the term liberally to mean someone who drives for a living) passing you with traffic coming the opposite direction.
busses, dump trucks, taxis, and semis have all either come close to or have run me off the road. A taxi clipped my shoulder with his mirror once. a bus ran me into a 5 foot deep ditch. trucks have honked or squeaked past me.
2.) SUVs obstructing other peoples view of you. For instance, you're on a 4 lane road and need to make a left and have an SUV or truck behind you. Getting into the fast moving lane to make that turn can be dangerous and is the only time I've been hit and taken down. Usually someone in a hurry, passing slow moving traffic very quickly.