Alcohol stats have nothing to do with passengers. However, a crash is "alcohol-related" if at least one driver had a BAC of .08 or higher. This overstates motorcycle "involvement" because of crashes in which the rider was sober but the other guy was drunk.
But NHTSA does report fatal motorcycle crashes in which the motorcycle rider was at .08+. In 2006, that was 27% of all riders involved in fatal crashes, vs. 23% for drivers involved in fatal crashes. More here: NHTSA 2006 Motorcycle Fact Sheet (750K PDF).
It's possible for a drunk driver to be involved in a crash that wasn't his fault and to be charged with the DUI but not the crash. Former Raider running back Marv Hubbard had that unpleasant experience a few years ago, when some (sober) doofus was killed when he made a U-turn in a blind turn on a dark road, and Hubbard, who had been drinking, hit him.
