The Center for Neighborhood Technology has done a lot of excellent work, including launching the I-Go car sharing program and advocating for cleaner air thru increased transit usage. One of my favorite CNT initiatives is this set of Housing + Transportation indices, including the wonderful maps of Household Auto Greenhouse Gas Emissions, which you can set for many regions. These clearly show that auto use diminishes as population density increases. It's hardly a leap, then, to argue that population density tends to decrease greenhouse gases. From that argument, it's one more small step to then claim it's good for the planet to point development toward projects that will host higher numbers of people on average over all times.
So, now we're back to PLUM (Popular Land Use Metric)* scores, which I introduced as an idea back in February. If we could estimate the number of people physically located on an acre on average over all times, then we'd have that acre's PLUM score. A land use with a higher PLUM score is, by definition, serving more people, which ought to count for something in the planning realm.
On Memorial Day, the New York City Department of Transportation closed several blocks of Broadway to automobile traffic. (A few articles about this made Streetsblog and that's where I stole this photo.) NYDOT is saying that they think this street closure will actually help move traffic, which sounds counter-intuitive. The theory is that Broadway is a diagonal street which creates more than its fair share of intersections. Every intersection has a stoplight. By closing certain blocks, there will be fewer or faster stoplights on streets following the grid pattern.
On the north side of Chicago, we have numerous six-way intersections and my experience leads me to believe that NYDOT has a point. Plus, there's not much harm done by closing some blocks of a diagonal street while keeping others open. It's usually quicker to avoid sections of Milwaukee Avenue or Clark Street and just drive west for a while and then north. Few people take congested areas of these diagonals for more than a couple blocks. They're not used as thru-streets like those following the grid pattern.
In any case, check out the photo and think about this in terms of PLUM scores. Sure, this was Memorial Day and there was a special event. But if this change leads to more people simply being on the space that used to be the automobile section of this block of Broadway-- on average & considering all times-- then that's an argument for keeping this carless.
*(I'm just using this name until someone tells me there's already a planning term that applies to this concept.)
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