It was a bad winter in Chicago and, frankly, pretty much everywhere in the Northern part of the country. If April showers bring May flowers, then January snows bring February potholes. Or at least that is the conventional thinking, but is Mother Nature really the only cause of potholes?
The article is written by Lucius Riccio who, among other things, is a past Commissioner of NYC’s Department of Transportation. His contention is that the formation of potholes is not independent of how a city treats it roads and that Gotham may just have been asking for a ton of potholes. Here’s the punchline to the article.
Clearly, fixing potholes is an essential and commendable thing to do. And to do so efficiently is a worthy management objective. Of course, it is not how many you fill but how many you don’t fill. Or put another way, how long do they remain in the street breaking axles and blowing out tires? But in addition, I think the fixation (pun intended) with potholes is the wrong approach.
A high number of potholes is indicative of a failure to maintain the streets. Fixing potholes means the smart thing hasn’t been done, which is to do the work that prevents them in the first place. Potholes are emblematic of a failed strategy.
How does he get to this conclusion? Data!
Turns out, New York City keeps lots of information on its roads. For example, this graph shows the fraction of streets rated as “good,” where good means seven or above on a ten point scale.
Note that the general quality of New York streets dropped over a decade or so but then leveled off. Mr. Riccio’s got an explanation for that. He estimates that New York needs to be paving about 1,000 lane-miles per year (where one mile of a four-lane avenue counts as four lane-miles) to keep street quality constant. If paving drops below 1,000 lane-miles, road quality deteriorates. If NYC goes above 1,000 lane-miles, then quality improves.
Here’s what the city has done paving-wise over the last several years.
Apparently the paving budget took a hit for a while before bouncing back up again. Less paving explains the drop in street quality. The return to 1,000 lane-miles per year explains how the city stabilized quality, albeit at a lower level.
Take the cumulative difference between what the city paved and the 1,000 lane-miles per year bogey as a resurfacing gap. What do you think happens when you graph the number of potholes repaired against that resurfacing gap?
It’s a little hard to read, but the formula there estimates that the paving deficit explains about 81% of the variation in the annual need to fix potholes. Snow alone only explains about 32% of the variation.
What to make of all this? Clearly there is a compelling case that street quality matters and that better maintained streets are more robust streets when the snow starts falling. Of course, that doesn’t mean that the New York should be aiming for perfect streets. There has to be some tradeoff between paving now and patching later. Trying to pave every street, every year would be both expensive and disruptive. However, it would seem that getting the streets of New York back to the level they were at in the late ’90s would make a big difference in the potholes that would need to be fixed.
1. For the uninitiated, OR/MS Today is the member magazine for INFORMS, “the largest society in the world for professionals in the field of operations research (O.R.), management science, and analytics.” Unfortunately, the good people at INFORMS have deemed this article so good that it is only available to members.