I don't believe studies have been done, and even if they had, as Pete says,
they may be error prone - so we're all guessing in the dark really.

For my part, I'll bet beginning and low-time pilots probably do make better
drivers, for two reasons : 1)Respect for rules and 2)Weather observation.
Some here feel weather is more of a "nuisance" in driving than anything else,
but it remains one of the most often cited contributing causes in accidents.
Pilots are simply less likly to be surprised by weather, or to launch blithley
into degrading conditions. They also ahve at their fingertips a whole palette
of tools to allow them to quickly and accurately assess weather situations.

As for respect for rules - well, that's why I said beginning and low-time
pilots. Too often, after a few hundred, or better yet a few thousand hours,
pilots begin to feel that all those pesky, meticulous rules are just for
smaller fry, and this attitude probably carries over into their driving as
well.

GF