On some of the narrow roads I ride on, I don't think drivers would appreciate me taking up another two feet of space to the left of me. I'm already giving myself 3-4 feet on the right which means they need to move into the opposite lane to pass within a reasonable distance (4 (to the right) + 2.5 (bike width) + 3 (to my left) = 9.5 in a ~10 foot wide lane). I do like the idea of turn signals though. I would use them if I had them.