Considering all cycling accidents, roughly 59% occur from the rider losing control of and falling from or crashing their bike... in other terms, single-bike crashes.
14% collide with a fixed object: a tree, telephone pole, wall, etc.
11% collide with a moving motor vehicle.
9% collide with another cyclist.
3% collide with an animal -- dog, deer, 'possum, etc.
2% collide with a pedestrian
1% are those blind Toms who run into the back end of a parked car, or who are "doored."