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Last week, Mayor de Blasio signed a law lowering New York City’s 30-miles-per-hour speed limit to 25. The change is the centerpiece of de Blasio’s Vision Zero plan to drastically reduce New York City traffic deaths, which numbered 291 last year. (To compare: The city saw 333 murders during the same period.) The majority of those killed were on foot when they were struck by cars or other vehicles, and the new speed limit is explicitly intended to protect pedestrians (even — or perhaps especially — the jaywalkers.) “When drivers are driving below 25 miles an hour, it gives them much more time to avoid crashes, gives drivers and pedestrians more time to see each other, greatly intensifies the opportunity to save lives,” said de Blasio at the signing, which took place at the Delancey Street intersection named after Dashane Santana, a 12-year-old killed by a minivan there in 2012.

The 25-miles-per-hour speed limit goes into effect on November 7. Here’s pretty much everything you need to know.

How often does New York City change its speed limit?

Never, really. It’s been 30 miles per hour since 1965. You’re about to witness history, though you might have to invest in a speed gun to get the full effect.

And when does this history happen, again?

Like we said, the first day of the 25-miles-per-hour speed limit is Friday, November 7 — just in time to annoy anyone driving in for a weekend adventure, not to mention cab drivers and their drunk, impatient customers.

Is it going to take a lot longer to get everywhere now? I’m already late.

If most motorists don’t just ignore the law — and that’s kind of a big if! — then, yeah, driving in New York City will probably take a little longer than it used to. A car traveling at the old speed limit will cover a mile in two minutes; a car traveling at the new speed limit will take an additional 24 seconds to do the same thing. A garbage truck, a manhole explosion, a street fair, a whole street blocked off for the filming of some TV show, a row of traffic lights that are out to get you specifically, and/or a garden-variety traffic jam can and will pop up whenever. You do the math.

Won’t a lower speed limit make every cab ride more expensive???

No. A yellow cab charges $.50 for every fifth of a mile it travels at 12 miles per hour or more. When the cab moves at less than 12 miles per hour, it switches to a time-based charge of $.50 per minute. Because this sounds like a word problem, you might be tempted to try to figure out how the reduction of cab drivers’ maximum (legal) speed will result in customers paying more for rides. Don’t embarrass yourself by following that impulse. A trip in a cab traveling at 25 miles per hour will not cost more than a trip in a cab traveling at 30 miles per hour, assuming you don’t hit traffic.

What about Uber?

Uber is secretive when it comes to how, exactly, it combines a car’s per-minute and per-mile rates when calculating a fare. The new speed limit probably won’t affect Uber prices, but a well-designed experiment is probably in order to make sure.

Is getting hit by a car traveling at 25 miles per hour really that much better than getting hit by a car traveling at 30?

Yes, it’s considerably better. Studies show that a pedestrian has a 37 to 47 percent chance of surviving a collision with a vehicle traveling at the old speed limit of 30 miles per hour. Figures cited by the de Blasio administration say that slowing that vehicle to 25 miles per hour doubles the likelihood that the person will survive.

But do your part to avoid getting hit by a car by at least briefly looking up from your phone before you cross the street.

So 25 miles per hour is the “default” speed limit. Does that mean there are places where it doesn’t apply?

Yes. Speeds of 30 miles per hour or more will still be allowed on parkways, expressways, and high-traffic “arterial” roads, such as Queens Boulevard and Staten Island’s Hylan Boulevard and Richmond Avenue. Meanwhile, school zones and other areas in need of what is called “traffic calming” will continue to have speed limits lower than 25 miles per hour. Streets with speed limits that are not 25 miles per hour should be clearly marked.

Still, there’s a reason they use the word default: 25 miles per hour will be the rule on about 90 percent of streets throughout the five boroughs. De Blasio has promised 3,000 new signs to remind people of this at airports, highway exits, and other entry points to the city. However, as with the old speed limit, drivers who don’t see speed signage of any kind (which is the norm) are expected to assume that they should keep it to 25.

Does the new speed limit apply to bicycles?

Yup, it’s just like the old one in that way. But the change isn’t likely to lead to a big crackdown on cyclists, who are also frequently hurt or killed when hit by cars. (One hundred thirteen pedestrians and 18 cyclists have died in New York City traffic accidents so far this year.)

Is this going to lead to a big crackdown on anyone?

Probably not on anyone who wouldn’t have gotten themselves into trouble for speeding before. When de Blasio signed the new law, he and NYPD Transportation Bureau Chief Thomas Chan suggested that cops weren’t going to be looking too hard for people going at one or two miles above the new speed limit. “The officer can use discretion,” de Blasio said. “They might see someone go 24, 25, 26 down to 25 again, and say that’s just a minor variation. But if someone’s going 26 miles an hour, and veering back and forth in the road, the officer has every right to give that person a ticket.”

Chan echoed the “discretion” bit and added that his officers are more interested in people “speeding at a higher level.” Still, he said, “That doesn’t mean we cannot issue you a summons at 26 miles an hour.” Be smart!



Will speed cameras also be allowed to use discretion?

Speed cameras are machines, so they’re pretty rigid about that kind of thing. However, the new speed limit won’t make cameras more likely to bust drivers. Right now, New York City only has them installed in school zones, which, as noted above, have their own (slower) speed limits. So, if anything, a lower default speed will make people less likely to end up with camera-issued tickets, which start at $50 for exceeding the limit by ten miles per hour. People who DGAF about school zones will continue to get tickets, as they should.