Ohio Department of Transportation officials say the state has 5,300 hillside areas at risk of sending rocks onto nearby highways and spends $16 million a year preventing or cleaning up slides.
A department spokesman tells The Columbus Dispatch all 88 counties have such areas. Crews are working in eight counties to stabilize hillsides or clean up after falls, and 37 summer projects are planned.
State engineer Jim Graham says hillsides were made steeper for roadways along Ohio rivers. Rock cracks fill with rainwater that freezes and melts, making it vulnerable.
Fixes include concrete barriers and roadside ditches to catch rock and road closures.
Slides gained attention last week in Athens when a sliding boulder weighing roughly 100 tons crushed a car and damaged a home, utility poles, and a water line.