Clown on a unicycle
One interesting experiment displayed how cell phones contributed to inattentional blindness in basic tasks such as walking. The stimuli for this experiment was a brightly colored clown on a unicycle. The individuals participating in this experiment were divided into four sections. They were either talking on the phone, listening to an mp3 player, walking by themselves or walking in pairs. The study showed that individuals engaged in cell phone conversations were least likely to notice the clown. This experiment was designed by Ira E. Hyman, S. Matthew Boss, Breanne M. Wise, Kira E. Mckenzie and Jenna M. Caggiano at Western Washington University.
I postulate that paying attention to a display in the car instead of on the road is pretty similar to this. I rest my case.