> it needs to be to force people to use dense housing and public transit or cycling/walking.

I never understood why people believe living in dense cities is good for the environment. Could you explain why you think so? I get the transit argument, but imho everything else points to the opposite. Cities are warmer than rural areas. They cannot store the water from rain, they have to transport it away. They have problems with air pollution, not only because of cars. They disconnect people with nature, because they cannot experience nature day to day. The air is much better outside of cities. You can't buy healthy food around the corner from the farmer that produced it, etc.