To the Editor:
As usual, it wasn’t us. It was everyone else in the room who was crazy.
It seems ingrained in politicians’ and engineers’ brains to never admit they are wrong. Ever. So much so that our local and County governments literally fought parents and residents for years in their hell-bent efforts to NOT protect the children of Bear Tavern Elementary School with the 25 mph speed limit the State law prescribes – the limit enjoyed by every other public elementary school in the County. Instead, for Bear Tavern alone, the County insisted on hiding behind an engineering rule-of-thumb that was never meant to apply to roads with safety concerns.
Where there isn’t a law or local ordinance setting a safety-based limit (as there is in New Jersey, where all schools are supposed to have a 25 mph limit during opening and closing; see RS 39:4-98), engineers sometimes consider the “85th percentile rule” found in the federal Manual on Uniform Traffic Control Devices (MUTCD). Out-of-touch engineers often tout this as a “scientifically sound” way to set speed limits based on what the configuration of a road itself tends to produce— if 85% of drivers on a stretch of roadway are found to travel at 50 mph or less, this method enshrines the speed limit at 50 mph.
For years, in fact, the speed limit in front of Bear Tavern was 50 mph. (The current limit is 45 mph, a reduction achieved after one of us analyzed police speed studies and found one that, under the 85th percentile rule, supported such a reduction.) Granted, the speed limit does drop to 30 mph (but not 25…) for brief periods during opening and closing, but it is still 45 mph during other vulnerable times – when kids are on the front lawn, arriving for early classes, leaving from late classes, etc.
Even Arthur Sypek Jr., former Mercer County Counsel, agreed with us. In fact, an OPRA filing revealed these 2013 emailed comments from Mr. Sypek to the County engineer overseeing the Bear Tavern area: “I am concerned about the County’s liability exposure if in fact we are not adhering to the school zone statute and there is an accident within the school zone. Our defense that we followed NJDOT standard engineering practice in establishing a higher limit will not be a defense to the County not adhering to the State law within school zones.”
But as of this month, it’s no longer just Kim, Adam, and many BT parents saying, “Hey, that 85th percentile rule is crazy”. Two Cornell University professors, writing in the current issue of the Harvard Law Review, say it even more strongly than that (https://harvardlawreview.org/2021/10/rewriting-our-nations-deadly-traffic-manual/). Their new paper calls for the complete revocation of the “85th Percentile Rule,” so beloved by our Mercer County Engineering Department. The professors clearly explain how the rule “permits the most reckless 15% of drivers to trigger an increase in the speed limit simply by breaking it,” and they call it “perhaps unique in American law in empowering lawbreakers to activate a rewrite of the law to legalize their own unlawful conduct.” The authors go so far, rightly, as to call the current manual “Our Nation’s Deadly Traffic Manual,” a sentiment echoed by a recent Bloomberg’s essay. (https://www.bloomberg.com/news/articles/2021-05-05/it-s-time-to-rewrite-the-road-builders-rule-book)
The data are clear; at 20 mph, a pedestrian has a 95% chance of surviving a collision with a car, but at 40 mph, that chance drops to 15%. So a school zone, (where there are young pedestrians and cyclists, but also dozens of cars with children, needing to slow to almost 0 mph to enter the driveway), is pretty much the last place one would want speeders to determine the speed limit. So yes, let’s end the fetish about the 85th percentile, but until then, let’s never apply it where the law and common sense say it doesn’t apply.
Meanwhile, the traffic on 579 just keeps getting larger and faster; better get over to Knights-R-Us, kids. We hear there’s a sale on armor.
Kim Robinson and Adam Finkel,
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