Injury crashes cost society more than $38 billion annually. Expending up to $2.3 million to prevent one fatal crash appears to be rational public policy, although the crash costs society only $500,000. Prevention of severe, non-fatal head and spinal cord injuries warrants even larger expenditures. The estimated rational investment to prevent an average nonfatal injury crash is $22,000, while society's cost is $8,000. Rational investment levels for increased safety are estimated by summing the amount individuals typically pay for small increases in their safety and the cost the rest of society bears when someone is killed or injured, including transfer payments.