I ran across this on the NHTSB board, so these are US stats
Note: The article is a few links downI remember the data from the Hurt report showed "about" 50% were single vehicle, 2005 data seems to show 44%. Still a very large percentage and something important to keep in mind ...Fatal Two-Vehicle Motorcycle Crashes
In 2005 there were 4,553 motorcycle rider fatalities, of which 2,021 (44%) were from single-vehicle crashes and 2,532 (56%) were from multivehicle motorcycle crashes. This report provides further data on both single and two-vehicle fatal motorcycle crashes.
feature arrow icon NCSA Technical Report (DOT-HS-810-834) (PDF)
A serious subject I know.