Same in a car, or fighter jet for that matter: Want to see the time? Look at where the clock is. Want to see what radio station you're listening to? Look at where the tuner is. Want to see how much gas you've got? Look at where the fuel gauge is. This is constant-time lookup. If you have multifunction displays that *change* where these basic things are, now you've upped the cognitive load on the driver in that he now has to keep track of what state the display is in rather than just glancing in a well-remembered spot.
Ford did a pretty good job of this in the Cmax hybrids. The things you need to know to drive the car don't change location, and are the way they've been on cars forever. The speedometer is a big analog rotating needle, so you just have to glance at the needle position-- you don't have to evaluate numbers. The hybrid details are also displayed as analog dial information (using the LCD) to minimize mental processing. They're also in an unobtrusive side display of the driver's side triptych and you can choose from several default sets of details that all are consistent with showing the same information in the same way, but add new information if you pick the more detailed ones. The center console is for phone, entertainment system, climate, and nav, and can be controlled via the touchscreen, traditional controls that would be familiar if all you ever drove before is a car out of the 60s, or voice controls interchangeably. The more common things to adjust also have steering wheel controls, but it's all set up so the learning curve is easy and you can operate everything just fine with all the traditional controls.
But yeah. If you've got bells and whistles and distractions in your field of vision, of course it's unsafe. Most people are probably smart enough to ignore the popup message crap polluting automotive mutlifunction displays, by keeping their eyes up. If the crap follows them there, that's not an usafe display mechanism, that's unsafe human interface design. </rant>
that's what bugs me whenever I drive a prius- they decided to get creative and put things in non-standard positions, used digital displays where analog is faster to evaluate, put a whole bunch of distractive stuff in the driver's field of view, and made the front window small with huge pillars so it's hard to see out. It's a car that encourages people to drive badly.