Guerrilla signage helps slow NYC traffic speeds. Actually enforcing traffic laws (really?) also seems to help.

Let's see. If citizens do it themselves, and the city does what it's supposed to be doing ...

A DIY Approach to Slowing a City's Cars, by Sarah Goodyear (The Atlantic Cities)

At first glance, they look an awful lot like official city speed-limit signs, bold black letters on a white background. "20 Is Plenty," they say.

Look closer, these signs are not NYC DOT issue. First, they're made of plastic, rather than aluminum, and affixed to signposts with zip ties rather than bolts. They are not reflective, the way real street signs are. And at the bottom, in white letters on black, is the logo of the DIY street safety action group Right of Way ...

City officials in New Albany might be more interested in these next two paragraphs, seeing as they've lately taken to insisting that laws to keep semi-trailer-pass-through traffic off downtown streets (i.e, weight limits) actually do exist, even if there exists neither will nor a plan to enforce them.

Vision Zero? Ironically, we have it here, too. We call it Zero Vision.

 ... The signs are headed up to Albany today as part of a lobbying effort led by a new group called Families for Safe Streets, led by New Yorkers whose children, parents, spouses, and other loved ones have been killed by cars. The group is calling for lower speed limits and aggressive implementation of Mayor Bill De Blasio's Vision Zero plan, which incorporates improved street design and tougher traffic law enforcement.

That last part seems to be ramping up already, with WNYC reporting that tickets for dangerous violations such as speeding and failure to yield are up as much as tenfold in February 2014 over the same month the previous year (although in some precincts, such as the 84th in Brooklyn, they were starting from a negligible base of only 10 total tickets for speeding, failure to yield, and ignoring a signal).