Not so much change the rules as be persuaded to revisit them.
Pedestrian safety has been addressed predominantly via "crumple zones", because that's what the technology could most reasonably entail and regulations were crafted accordingly.
Persuade bureaucrats to revisit those axioms, in light of technological developments which were impossible prior, with actuarial data proving superiority of the new technology, and bureaucrats are happy to cautiously deign to change the rules.
To wit: USA sees about 6000 pedestrian/car fatalities per year; if, say, Tesla were to demonstrate a technology demonstrably reducing pedestrian fatality rate equivalent to 600 per year, bureaucrats would be hard-pressed to not approve that alternative tech via rule changes.