Grant Petersen was in town a few week's ago promoting his book "just ride" we were talking about the value of "acting a bit strange" while riding your bike. When you hear someone coming up behind you he suggests a not so subtle action on your part that gets the drivers attention - NOW what you choose to do should depend on the traffic, speed, etc. For example, perhaps you wave your left arm in a crazy way, or if they are back far enough and traffic is slow you actually swerve out more into the road. It is quite effective. We have started to practice this on a regular basis - we don't put ourselves in danger but we will throw out our arm or take more of the lane and suddenly the car or truck will move over (how cool is that) So instead of being Ms nice and hugging the right side of the room, take you place and act a bit crazy They will be talking about the crazy chick on the bike but at the same time we may do more to educate drivers about being aware that way.