I was riding with my son last night... we both had helmets, lights front and rear. We came to a stop sign, and wanted to turn left. A car came up on the other side of the intersection, at about the same time as us.
So my son runs the stop sign , and starts his left turn! In the dark, with no way to tell if the car had really seen us! (could not see driver's face) I was stunned, and yelled, "DON'T GO!" He slammed on the brakes as if shot. When his foot touched the pavement, and my foot touched the pavement, the car took the body language and proceeded forward normally through the intersection.
He's a smart kid, and a good rider... but he's only 14. His judgement and understanding can vary from excellent to not worth $hit. That's 14 for ya.
We're going to have more discussions about left turns in the near future.
TEENAGERS... sometimes I can't wait until he goes to college.