Increasing density will naturally decrease reliance on personal motor-vehicles because more journeys become walkable.
Only if you don't need to go to work. Which is working wonderfully in pandemic era. I can pretty much walk anywhere I could need in terms of stores and services.
But jobs, unless you work in one of those stores or services, are of course far away, not in the middle of denser housing. Tech company campus won't be between housing rows.
My town has built tons of housing over the last two decades. Offices are still in the industrial campuses farther away and all that new housing means tons of new local traffic. Uncomfortable but true.
It used to be 2 minutes and one stoplight to get to the highway. Now it is 7 stoplights and up to 15 minutes to get to the highway (from the same house).
It would be wonderful if for every new housing block there was an adjacent office complex block, so most people can walk to work, but that's not how it goes. So in practice, yes, increased housing density just means tons new traffic to fight through.
Hopefully I can just remain work from home forever!
Now it’s possible (maybe) for many more people (although they’ll need larger housing units).
Fancy way to say 'car'.