At that price, only state transportation departments can afford them, and they usually measure only major highways. American cities (and Ramallah, near Birzeit University, for that matter) rely mostly on citizen complaints or seat-of-the-pants assessments by city employees.

That unscientific approach presents problems, said Glenn Engstrom, the director of the National Road Research Alliance, which conducts pavement research at MnROAD, the Minnesota transportation department’s asphalt test track.

“People are far more tolerant of bad roads in urban settings, because speeds are lower,” Mr. Engstrom said. He noted that apps like Carbin could be particularly helpful in cities because those expensive vans don’t work as well in stop-and-go traffic (or in freezing weather, a.k.a. pothole season).

Accurate data is better than citizen complaints for road maintenance. The time to resurface roads is when the roughness index starts to climb, even before drivers report problems.

“Smooth roads last longer,” Mr. Engstrom said, “and that definitely helps both the environment and our pocketbook.”

Upon his return from the West Bank, Professor Ulm bemoaned the lack of roughness-index data on those roads to another engineering professor, Arghavan Louhghalam of the University of Massachusetts, Dartmouth. It occurred to her that the accelerometers built into smartphones might be able to measure road roughness.

From that initial conversation, they assembled a group of five faculty supervisors from M.I.T., UMass Dartmouth and Birzeit University. Six students from M.I.T., Birzeit, Harvard, UMass Dartmouth and the University of Washington then went to work under Jacob Roxon, a Ph.D. candidate at M.I.T.