The HUD itself would help to keep the focus of your eyes more in proximity of where you are traveling. What tends to cause distractions are all the ancillary things like entertainment, navigation and communication. I would say that BMW's iDrive works best with the interface since one can learn commands via a series of movements and clicks - it's not perfect by any means, but for most primary functions, it's better than trying to touch a screen. The more involved the command, the more likely it is to distract - such as entering a navigation destination manually. Voice commands still have a long way to go, and each manufacturer tends to use different command keywords - it's not natural language yet.