the roads in and around the cleveland metro area have high traffic loads; undergo long periods of fluctuating cold temperatures during the winter; and get nailed periodically by lake-effect snow and ice.

as such, they experience lots of freezing and thawing, experience high traffic from lots of tractor trailers and snow plows, and get coated with de-icing materials (salt, or more recently sand-based grit in some areas). synergistically, these conditions are extremely rough on paved roads, so potholes are ubiquitous and painful.