The difficulty in knowing what the stats are in people just getting stoned then driving and crashing is knowing whether they smoked two weeks ago or just finished puffing a huge blunt.

However in most cases where they find weed in the DUI offenders system, theres usually alcohol too

Regrettably I know what it is like to be quite under the influence of each while driving. Alcohol makes cocky, weed makes you cautious, the latter is a much better attitude to drive with