can't understand the downvote but i found the reg.
FMVSS (not sure if this is written by NTHSA or what) requires bumper to be 16-20in for passenger cars and max 28in for light trucks. This then effectively dictates the minimum hood height.
I additionally found a voluntary program in Eu called EEVC around bumper, hood and windshield design factors to reduce ped injury. NHTSA also has pubs around it but in the time I'm willing to invest I couldn't find if these are required or even voluntary or what in the US. Nice, brief summary article with diagrams from 2002: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1123098/
FMVSS (not sure if this is written by NTHSA or what) requires bumper to be 16-20in for passenger cars and max 28in for light trucks. This then effectively dictates the minimum hood height.
I additionally found a voluntary program in Eu called EEVC around bumper, hood and windshield design factors to reduce ped injury. NHTSA also has pubs around it but in the time I'm willing to invest I couldn't find if these are required or even voluntary or what in the US. Nice, brief summary article with diagrams from 2002: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1123098/