Not Approved by California DMV

Heads-up displays are coming into cars very quickly. Right now, they only display speed. The goal is to put information right in the driver’s field of view to minimize eye movements away from the road.
This makes sense from a cognitive perspective, except for one major flaw: people can only pay attention to one depth at a time. Therefore, attention must shifted from the road (relatively far away) to the windshield (much closer) in order to glean necessary information.
more HERE