Improvements to emissions from density are non-linear. Pretty interesting.
For everyone's information, Providence is at around 9,000 per square mile. In a northeastern context, this doesn't feel very dense at all. But on this curve, we're well on our way to better emissions goals, and quite a bit denser than a lot of other cities in the country. Big world leaders like Zurich, Switzerland are only at 11,000 per square mile.
The other thing that the study finds is that emissions are not just affected by density, but are heavily affected by how streets are laid out, e.g., whether there are decent biking facilities, if zoning allows mixed-use places, how frequent transit is. As I like to point out, Groningen, Netherlands, is less dense than Providence, but has sixty times the per-trip biking than Providence has (60% vs. 1.2% of trips).
Providence benefits from having a number of its suburbs being relatively dense too--some, like Central Falls, are denser than Providence. The East Bay, Pawtucket, Attleboro, and even parts of Cranston can help us meet these goals with their layouts as well, because they are also well on their way. We have good connections to Boston and Newport by bus or train.
Providence, with its good density levels and available land for new development, could densify further, add more non-car options, and really be a leader. Check out the study report here.