A helmet cam or some type of video camera will defuse most road ragers. Just tell'em to smile for the camera. A camera in the back is also a good idea.
http://www.youtube.com/watch?v=QSiBVTtrS1w
http://www.youtube.com/watch?v=6qycF...eature=related
http://www.nytimes.com/2012/07/21/te...ents.html?_r=1
http://www.alibaba.com/product-gs/52...camcorder.html