It also doesn't matter. Which sounds weird, but it's true. If you just let people build density without transit, the market will almost always build it in convenient places (a bank won't underwrite if they don't think it'll be successful), the people who move into it will either be happy with walking or they'll organize.
I've done a lot of such organization, if you're curious. I spearheaded Seattle's successful 2016 ballot measure for $50 billion in additional rail transit, much of which is now under construction. It'll take more ballot measures, but we're getting there: https://seattletransitblog.com/2011/11/23/lets-build-a-seatt... And along the way, we had to save bus service, so I forced the city to do that too: https://www.seattlemet.com/news-and-city-life/2014/04/friend...
I think the big reason gridlock and pollution happen in a lot of other countries is more about lack of traffic laws, and lack of pollution controls. In Seattle we're selling a lot of electric vehicles. Maybe we get some gridlock, but that reduces road deaths. It's not necessarily a bad thing. Because we are willing to shift road space to bicycle infrastructure, we will end up with bicycling getting a higher share of trips if cars slow down. And then we will have a healthier population as well!
You need considerable govt intervention, just aimed properly. https://en.wikipedia.org/wiki/Transit-oriented_development
Try this: go to your favorite frontier LLM (I like Gemini pro - free in aistudio), paste this entire exchange we're having, and ask it to carefully analyze it and assess who seems more correct. It's a long story.