Magic Shine lights will give you the best bang for the buck, period. It's worth waiting a couple of days for the delivery. Also, consider some reflective materials: patches, strips and powerful rear blinking lights as well. The yellow reflective Velcro ankle strips are eye-catching since they move with your legs.

The drivers can see you just fine when you're on the side of the road. Or should I say, the drivers WILL NOT see you anyway until you roll over their hood and even then they'll wonder where the hell you came from. I'd stay on the side, to be out of their way, just in case. But that's me. There are more drunks at night too.