We should be warned.

I had an idea when driving back from my wife's Aunts cottage....

We need to create a system where by if the person driving in front of you is doing a speed which is less or more than the posted speed limit it would flash up on the rear window.

We could have these messages:
+ 30 kph "I have a death wish and am going to take somebody out"
+ 20 kph "I am late and need to get there..."
+10 kph "I know this road, and know you are behind me."
0 kph "I know what I am doing, but need some space to drive safely."
-10 kph "I am just wondering around and not really thinking about what I am doing."
-20 kph "I am scared of driving and you should really be at home or riding in a cab."
-30 kph "I am either drunk, texting, yelling into my phone, or too scared. Please call the police"
-40 kph "Please push me off the road and call the Police"

I was thinking about this as driving along a road where the tire tracks were on bare asphlate and the person ahead of me was doing -30 around the corners and then speeding up to -20 on the straight parts and I was becoming annoyed with them and knew I would be safe at +10 driving. So the person cost me an extra 30min on my drive, and about $5.00 in fuel. Though I was safe and got home.

I did pass by about 4 wrecks in the ditch. But there were all single car accidents.