And I have statistics on my side. 80-90% of all accidents are avoidable. Therefore, the most effective safety measure by far is to be a truly GOOD driver.
Seatbelts may, in fact, contribute to accidents, if the theory of risk homeostasis is correct.
However, their effectiveness is really irrelevant. The real issue is that seatbelt laws, helmet laws, and child seat laws are all wildly unconstitutional.