Time to lower speed limits?

Vox reports on a new law in New York that gives New York City the authority to lower speed limits:

Sammy’s Law allows city officials — rather than the state’s Department of Transportation — to determine the speed limits on their streets with input from community members. The bill will allow the city to drop the speed limit to 20 miles per hour on some streets in an effort to reduce pedestrian deaths.

I hate hate hate this. 20 mph! You might as well be riding a tricycle.

Also, I hate laws named after a child. It's usually a dead giveaway that it's the product of browbeating by some tiny but psychotic group of parents, not reasoned thought.

And yet, the fact that I hate it doesn't mean it's wrong. In Europe, the normal residential speed limit is 18 mph,¹ and they have way fewer pedestrian deaths than we do. I'm sure we could all get used to it too.

Personally, I still hate the idea. But that doesn't make it a bad one.²

¹That's 30 kilometers per hour in commie units.

²Plus I've never really understood why New York City has so little autonomy in the first place. Why does it have to get state approval for so many things? Good idea or not, I can't think of any good reason why they shouldn't be allowed to set their own speed limits.