I'd try calling the FHWA Resource Center, or the crash testing facility of your choice, such as Texas A&M, Midwest Research Institute, etc.
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928
"I'm searching for the questions, so my answers will make sense." - Stephen Brust
It applies to all vehicle barriers; atop retaining walls, in parking garages, etc. It is also contained in many codes (IBC, Florida Building Code, etc.)