In 1966, there were 50,895 traffic fatalities reported in the US. 2003 (the last year for which I have data) was a little better at 42,643. Has the effort and expense of engineering seatbelts/shoulder harnesses, airbags, door beams, energy absorbing materials and soft cushy radio knobs been wasted?
Nope. Fatalities per 100 million vehicle miles travelled has dropped from 5.50 in 1966 to 1.48 in 2003 -- an almost fourfold improvement (3.71-fold to be precise while sounding stupid). When fatalities are compared to resident population, licensed drivers and registered motor vehicles, the numbers are also quite remarkable.
Data from NHTSA Traffic Safety Facts 2003 (PDF).