Fifty-one years ago, on March 19, 1969, (I learned in 2016) the US DOT was recorded as saying that they intended “after technical studies have been completed, to extend the requirement for underride protection to the sides of large vehicles.”
They have not done so (even though it has been proven possible & technicalstudies have been done) — just like they have not mandated rear guards to be stronger or front guards to be installed.
On March 19, 1969, I was thirteen years old. Little did I know about what they had said or that in 8 years I would get married on March 19, 1977 (43 years ago today), that in the ensuing years I would bear nine children, teach them at home, raise most of them to adulthood, and bury two of them due to preventable Death By Underride.