I posted something (only I think it was on another forum) about horses pulling back and how to fix that. If I can find it, I will re-post here.

After he has gotten SUPER DUPER comfortable with the baggie grab he blanket and shake it around all over him (same principle with the baggie, consistent speed, distance, go with him etc.) I would start on both sides and eventually move to his head (stay away from the rump) but DONT put the blanket on yet. Basically, it's an extended version of the baggie. Once he gets used to it shaking everywhere and knows it is nothing to be afraid of (unfortunately I dont have a time frame for this as every horse and situation is different, but you seem to know your horse rather well so you should be a good judge) the next step is to put in on him. I will cover that when you are ready.

You're doing great, keep it up!

Oh yeah and P.S.- I would be scared of traffic too! lol