How can you stop bike accidents?

If by bike you mean bicycles then seperate roads/cycleways for them would be an excellent place to start. Most european cities and towns have dedicated bicycle paths and in more advanced places complete with their own traffic lights, etc. Physically seperating dyclists from other road users would massively reduce (but not stop) accidents happening.

If you mean motorbikes then there is not much you can do apart form encouraging bikers to wear clothing that is far more reflective than the current "uniform black" simply to make them more visible to other road users. Also bikers need to learn that they have to have more respect for other road users and that just because they can fit through that gap doesn't mean they should.