I've always thought that part of the reason for road-rage is a lack of communication possible between drivers.
The only way you can effectively pass a message to another driver is by way of horn or lights... and both are generally considered aggressive (even when not intended that way).
Now, imagine if all cars were fitted with something like CB-radio, but car-specific (perhaps a transponder code identical to the registration number). Imagine this could be done:
Driver behind: "Excuse me, would it be any bother if you could let me past?"
Me: "To tell the truth, I would rather be driving more quickly but this is the speed the traffic in front is driving at"
Driver behind: "OK, well what speed do you intend on driving at once the road is clear?"
Me: "I was thinking 75, maybe 80"
Driver behind: "I was hoping to go about 90... do you think you could let me past when it's clear?"
Me: "Sure, no problem!"
Now wouldn't that have been much more productive and less stressful?
Also, the increased communication would help get rid of the "I'm in my private metal-box" mentality that we are all subject to.