"A British auto insurance company said on Tuesday that in-car GPS navigation systems might be doing more harm than good by distracting drivers. Even more surprising, the company's findings suggest that navigation systems could be more disruptive than trying to read a map at the wheel. The findings, released by Privilege Insurance, showed that 19 percent of drivers who used their GPS lost concentration while driving, compared to 17 percent of map readers."
Funny thing about studies, they are either obvious or wrong. In this case I think it is obvious. Messing with a GPS while driving is very distracting. With a map at least you can see everything at once. The tiny GPS screen requires much more attention to find what you want. What do you think?