Hmmmm. attached is
A Guide To Federal-Aid Programs And Projects
there is some great information about Federally-funded Uniform Highway Safety Programs at the Federal HighWay Administration website [lots of digging in USC and CFRs required]:
http://www.fhwa.dot.gov/programadmin/proggd2.pdf [view pages 75,76 as
numbered in the text, not in the PDF server].
This seems to be part of the Federal-State Transportation Plan; it
looks to me like funding for safety enFORCEment.