If vehicle permissible speeds were based on permissible kinetic energy, then the desire for speed would become downward pressure on vehicle weight, which then requires a smaller, lighter battery, which costs less.
For freight, there would be pressure to use optimal vehicle and mode, which would favour rail for longer journey legs, which is easier to electrify than kitties. Lorries, actually, but autocomplete / spell check is sometimes too funny to correct.
Limiting kinetic energy limits the energy dissipated in a collision, which allows safety to be maintained using a less strong structure, which weighs less, which needs less energy to move around, which needs a less powerful motor and a smaller battery, and so less weight.
And so sustainable transport was solved.