Given the entire urban planning political environment has shifted towards gradual but substantial infrastructure changes, at this point the main barrier to change is just making it happen. And to achieve that all you need to do is push for new road standards and guidance at a city, county, or state level.
Once that's done the changes can roll out whenever there's maintenance or road widening going on. This is for example what Florida is doing to push for a comprehensive passenger rail system and it's what other countries have done to make their roads and streets safer and more efficient as well. So it'd stand to reason the same principle would work at state and local levels in the US for this as well.
The only real argument against it I could see is that it'll take too long but 30-50 years really is nothing for widespread infrastructure improvements.
Once that's done the changes can roll out whenever there's maintenance or road widening going on. This is for example what Florida is doing to push for a comprehensive passenger rail system and it's what other countries have done to make their roads and streets safer and more efficient as well. So it'd stand to reason the same principle would work at state and local levels in the US for this as well.
The only real argument against it I could see is that it'll take too long but 30-50 years really is nothing for widespread infrastructure improvements.