I'm not an expert when it comes to roads and highways. I mean, usually we talk about bike lanes around here. But today I learned, via Brian Potter over at Construction Physics, that there is such a thing as an International Roughness Index (or IRI). In simple terms, it measures how much a car bounces up and down over a given distance of driving, and it is usually expressed in units like "millimeters per meter." A low IRI is good. It means less bouncing up and down. And a high IRI is bad. It means more bouncing up and down, suggesting the road is poor. This, it turns out, is the most commonly used index in the world for evaluating whether a road sucks or not.

And in this recent post, Brian uses the index to chart out road quality across the US. Here's non-interstate roads for the 19 largest metro areas:

At least two things can be readily gleaned from the data in his post. Number one, US Interstates tend to be pretty good. More than 80% of the mileage is classified as "good" or "very good." Non-interstate roads are, on the other hand, much poorer. And in every single case, urban roads are worse than rural roads, presumably because of their higher traffic volumes. Number two, there doesn't seem to be much of a correlation between climate and road quality. Intuitively, one would think that freeze-thaw cycles and road salt would give cold cities the worst roads, but that is not actually the case.

Los Angeles sucks the most.

Cover photo by Thaddaeus Lim on Unsplash

I'm not an expert when it comes to roads and highways. I mean, usually we talk about bike lanes around here. But today I learned, via Brian Potter over at Construction Physics, that there is such a thing as an International Roughness Index (or IRI). In simple terms, it measures how much a car bounces up and down over a given distance of driving, and it is usually expressed in units like "millimeters per meter." A low IRI is good. It means less bouncing up and down. And a high IRI is bad. It means more bouncing up and down, suggesting the road is poor. This, it turns out, is the most commonly used index in the world for evaluating whether a road sucks or not.

And in this recent post, Brian uses the index to chart out road quality across the US. Here's non-interstate roads for the 19 largest metro areas:

At least two things can be readily gleaned from the data in his post. Number one, US Interstates tend to be pretty good. More than 80% of the mileage is classified as "good" or "very good." Non-interstate roads are, on the other hand, much poorer. And in every single case, urban roads are worse than rural roads, presumably because of their higher traffic volumes. Number two, there doesn't seem to be much of a correlation between climate and road quality. Intuitively, one would think that freeze-thaw cycles and road salt would give cold cities the worst roads, but that is not actually the case.

Los Angeles sucks the most.

Cover photo by Thaddaeus Lim on Unsplash