The
further reading section of the Wikipedia page has some decent info:
https://en.m.wikipedia.org/wiki/Pedestrian_safety_through_ve...TL;DR it’s about being low enough to not smack people of different heights in the head and cause massive acceleration of their brains against their skulls. Same with internal organs, and for legs it’s more about having some of that energy transferred into rotational energy, then having a soft-enough bumper and hood to again minimize acceleration forces and energy transfer.
There are also airbag-based solutions where it either inflates under the hood to give some cushion for the hit person to decelerate more gradually before stopping against something less forgiving, or kinda like a giant couch / Wacky Races cartoon catcher’s mitt inflating on the hood and front of the vehicle before they’re actually hit.
The pushback is, of course, mostly cost-based.
https://www.thetruthaboutcars.com/2007/12/the-truth-about-eu...
https://americawalks.org/vehicle-safety-for-pedestrians/
I just wish that the US would stop allowing people to build and operate killdozer pickups with bumpers well above where other vehicle bumpers are. When those crash into other vehicles, the other vehicle ends up with a differential, tires, and probably skid plates smacking into their vehicle, which it’s not designed to handle. Combined with how larger tires require more braking power to slow at the same rate, plus modified suspension geometry, higher CG, increased weight, and decreased driver intelligence, it makes for a much more dangerous vehicle for others to be around. Why do we continue to allow this, just like all the obnoxious modified exhausts and ECU tunes that massively increase the pollution being put out by one vehicle so they can feed their egos and intimidate other road users?
Higher bumpers are also a lot less safe for pedestrians, obviously: https://pubmed.ncbi.nlm.nih.gov/15949454/
Stuff like this has no legitimate purpose off-road and no business being operated on public highways: https://www.tiktok.com/@leanqueen6.7 but it’s become some idiotic macho culture thing.