How good are American roads?

This is a great analysis but it does focus exclusively on ‘roughness’, which is obviously important but isn’t the be-all-end-all of road quality.

One area I notice in particular that roads in the northeast US subjectively feel worse than Europe is in quality of road markings. Constant plow scraping and harsh salting seems to destroy markings.

I think it also shows up in the overall fit and finish of road infrastructure - edging and barriers, signage, lighting, maintenance of medians, how curbs and furniture contribute to junction legibility… and of course bridges.

One major reason is that European countries typically have national road agencies and consistent standards across the country (because, generally, smaller and less federal). US’s patchwork of federal, state and local road maintenance leads to vastly different budgets and department priorities across the network.

While I agree on your additional criteria, I feel the roughness metric itself (at least as explained here) is not as informative as it could be: a generally smooth road surface with sudden discontinuities in level (e.g.potholes) seems qualitatively worse (and damaging) than would be a smoothly-varying one with the same roughness. Perhaps an alternative metric might be based on the maximum speed at which a typical car or truck could travel without experiencing vertical accelerations above a certain threshold? ('typical', here would be with regard to things like its mass, suspension travel and stiffness, and wheelbase.)

The metric might already account for the scenario you bring up, since a road with potholes will be more 'rough' than a smoothly varying one based on my understanding of this metric.

I thought about that, but this is what I had in mind: take a section (say 100 M) of an undulating road, smooth it out, then put a ridge across it that restores its roughness to its initial value. My feeling is that the latter would be more of a problem (this opinion is colored by the fact that, in my neighborhood, road repair is creating bumps and ridges like this.)