There are some drivers that basically adhere to the law of the jungle, which is that if my vehicle is bigger or more banged up than yours, then I have the right of way. This definitely applies to 4-way stops and roundabouts. So the only thing that will cause these drivers to yield the right of way, or simply come to a full stop at signage, is some sensory input that is too ominous to ignore. Like the prospect of getting hit by a freight train.

Second, many drivers have a lot of other things on their minds, including a nursing a GPS screen, fiddling with the radio, talking on the phone, applying makeup, eating, changing a diaper, reading the paper and text messaging.

So a awe-inspiring spectacle of lights like the Second Coming/Judgement Day may be required to overcome this already taxing sensory overload. Unfortunately this may become a necessary arms-race of attention getting, where it may someday require the equivalent to a thermo-nuclear explosion to get drivers attention.