A major cause of fatal crashes is: Do you currently have car insurance? Insurance is mandatory to drive in Ohio Yes I have insurance. But please show me your best quotes. No, please help me find the best insurance. Question A major cause of fatal crashes is: Answers Inappropriately honking a horn. Driving too fast for conditions. Following a large vehicle. Explanation Driving too fast is a major cause of fatal crashes. A driver should always be ready to adjust their speed to changing driving conditions.