I can see the speed of traffic Im merging into, pedestrians, change of speed/flow of traffic ahead of me, and if a pedestrian appears to be willing to cross infront of me.
Without even having to think about it, I can just notice when there is emergency vehicles around or construction vehicles or any other danger-sign on the road. I can be talking to my passangers, listening to music or day-dreaming but would not miss any signs - its in the automated system already.
For me, having those kind of HUD stuff would just be even more redundant information to learn to automatically filter out/make judgements on.
In fact, I think such a heads-up-displays everywhere with color information, would just confuse drivers more and lead to more accidents - now you not only have to keep eyes on the road/let brain handle the information and do its thing - but also interpret and learn the various displays and what they mean, but also to confirm what they display to the sorrounding. More info to process - more error prone decisions.