http://www.cnn.com/2005/AUTOS/05/26/...udy/index.html
Northeast's drivers least able to pass basic written driving test.
Though, that may be more about non-enforcement of laws, and a substitution of a different set of rules -- one which makes it acceptable, for example, to pull into a right turn lane at a stop light/stop sign and then speed ahead and cut off the driver in the straight-ahead lane.