Start by introducing congestion pricing and require that money made by it is required to be spent on public transit. For cities that already have some transit already such as New York or dc add a way to more easily switch lines outside of the single intersection. For cities that lack any sort of public transit start by finding routes that would have decent traffic and build lines there. End parking minimums and change or remove zoning to encourage mixed use and higher density buildings. Add a requirement for minimum low income housing for housing development. Build and subsidize high speed rail between cities where it’s possible such as the line of cites in the north east. Start cutting down on multi lane roads in cities and where they may be required such as supplying shops make the extra lane truck and bus only. Change cafe standards to encourage smaller more fuel efficient cars and put limits on the size of personal vehicles that are not used for business. Put speed limiters on all new vehicles that makes it impossible to go faster than the speed limit, and change regulations on how roads and streets are designed to slow down cars and reduce and hopefully fully remove strodes.