A friend of ours was taken out broadside at an intersection- he was wearing screaming yellow vest with reflective, bright pants and a bright top. It was an overcast but bright day (so no deep shadows) and no trees or anything. He got collected, rolled right over the roof and broke his kneecap. His bike got dragged 200m before falling off the car- the car didn't stop.

I think it really doesn't matter how bright or reflective the clothing you wear (although wearing all black is just wrong), unalert drivers are not going to see you. I always ride in a group. Its easier to miss/ignore a single cyclist.