Is the saying "all accidents are preventable" true?

Taking precautions does not contradict belief in divine decree (Qadar); rather, it completes it. The statement "all accidents can be prevented" is incorrect in the context of belief in divine decree and destiny (Al-Qada' wa Al-Qadar). The correct approach is to qualify this with God's will, so one should say: "all accidents can be prevented, if God wills," in emulation of His (the Almighty's) saying: "And never say of anything, 'Indeed, I will do that tomorrow,' Except [by adding], 'If Allah wills.'"