[vkou]

It depends. Most people commuting to the office aren't living in a high-density downtown, anyways - they are trading a suburban home in the outskirts of the metro for a suburban home further out in the metro. The carbon footprint of the home is similar, the carbon footprint of their car will probably go down, as they only need to drive to the store/school/for social visits, as opposed to that, plus to work.