>I can only recall 3 forced upgrades, passive passenger restraints, which turned out to be airbags. Minimum MPG, across all cars sold (SUVs could be worse as lo

>I can only recall 3 forced upgrades, passive passenger restraints, which turned out to be airbags. Minimum MPG, across all cars sold (SUVs could be worse as long as other models improved). and crash survival, which turned out to be crumple zones. This is a bad way to frame it. All of those things have dozens to hundreds of downstream effects on the rest of the system. Large components (say nothing of sub assemblies) of a 1990 car could not be used in any practical way to build a road legal 2021 car (without comically inefficient workarounds) because the design revisions needed for modern regulatory compliance between then and now are so extensive. Heck, the physical dimensions of a typical 1990 car probably preclude compliance with current pedestrian safety requirements. There were also dozens of minor revisions to the regulatory standards cars must meet in that time (headlight performance, noise emissions, etc).