The problem is really not cars, but (if any) the way they have to be built. You could easily fit 4 people in a 400kilo vehicle on 2,5m length and move them safe

The problem is really not cars, but (if any) the way they have to be built. You could easily fit 4 people in a 400kilo vehicle on 2,5m length and move them safely at speeds of up to 100km/h. But crash regulations are so strict and the buildable types of cars so restricted that we all have to have the heavy, expensive, has driven cars that we now have.