Here's an unpopular opinion.
If car speeds maxed out at say 55mph, they could be much cheaper and safer and require far less regulation. I rarely hit 75mph, so why do all cars need to hit 120mph?
The only reason cars need so much crash protection is because someone might hit you like a 3000lb missile.
Engines could be simpler, fuel consumption lower, roads would be quieter, and fewer lives lost. No new innovation needed, just lower speeds.