Canada

Close-to-cause solutions have to start at municipalities. Yes, provinces and federal government can help, but municipalities can solve things quicker.

If I had full control in a large city:

• Primary mass transit would be expanded to increase the feasible housing areas
• Building permit offices and zoning authorities would get a complete overhaul, drastically increasing multi-unit housing in preference to single-family dwellings
• A graduated zoning system would be put in place so multi-unit housing was radically increased near mass transit (near 100% of permits). If people want single-family homes, they would have to live further away from transit.
• Downtown cores would increase pedestrian-only areas
• Tax rates for single-family homes would be increased substantially while condos and townhomes would be seriously reduced.

Basically, make single-family homes less appealing for a variety of reasons.