Yes, they did, summary conclusion on page 62 -
http://www.distraction.gov/download/811757.pdf
The results from this study present a clear
finding: VM subtasks performed on HH cell phones
degrade driver performance and increase SCE ris
The results from this study present a clear finding: VM (visual-manual) subtasks performed on HH (hands free) cell phones
degrade driver performance and increase SCE (safety critical event) risk.
I stand by my statement, that it has been studied and I'd hate to see funds wasted on enacting useless legislation when pre-existing laws can be enforced.