90% of cyclist deaths are caused by careless motorists.
An analysis of police reports on 2,752 bike-car accidents in Toronto found that clumsy or inattentive driving by motorists was the cause of 90 percent of these crashes. Among the leading causes: running a stop sign or traffic light, turning into a cyclist’s path, or opening a door on a biker. This shouldn’t come as too big a surprise: motorists cause roughly 75 percent of motorcycle crashes too. -- NYTimes
Here's the study the NY Times is talking about.
Drivers like to complain that cyclists are dangerous, but the numbers show where the real threat lies. Increase your visibility, get the attention of motorists and you're less likely to be run over. It's that simple.