A friend of mine had a plan for traffic control where everyone with a driver's license gets three paintballs and a paintball gun for their entire driving life. Folks police the bad drivers themselves. This way, if a cop sees a person with three paintball splots on their car, he can pull `em over and take their license and car away on the spot. It'd also make people more courteous, knowing if you pissed someone off enough, they could splot you and stick you on the bus for the rest of your life.
This was discussed in the science fiction short story by Lester Del Rey, "Why Johnny Can't Speed."
Essentially you take the right to self defense to the national highway system with 50 cal machine guns, dropable highway mines, rocket launchers, and luxury paint armor.