It found that a driver’s reaction times slowed by 46% when he or she was making a call on a hand-held mobile, by 37% when texting while driving and by 27% during hands-free calls.  For those on the drink-drive limit of 80mg of alcohol per 100ml of blood, reaction times were reduced by 13%. For those who had used cannabis it was 21%
~ Transport Research Laboratory (TRL), UK