That was the most motor vehicular related deaths ever recorded in a single year in the USA, in 1972.
The federal government proclaimed motor vehicular deaths as a public health issue and has since thrown billions of dollars at the problem. And it worked! Not only have those deaths sharply decreased to 32,675 in 2014, they have done so despite the fact that we now drive many more miles with more cars on the road. There has been nearly a 215% increase in the amount of miles driven since 1972, but the mortality rate has dropped over 40%.
That is a truly amazing thing and many people consider it the greatest achievement of the public health works of the 20th century.
That’s difficult to quantify, so I won’t try, however it is still amazing.