Driving on roads covered with ash can be hazardous. Ash is slippery, especially when wet, and moving vehicles constantly stir up the ash to create billowing clouds that significantly reduce visibility. These hazards can be reduced by driving slowly, but conditions (and accidents) may force temorary road closures. In ash-covered areas, travelers can become stranded for several days and supplies and shipments may be interrupted for days.

Ash that fills roadside ditches and culverts can also lead to poor drainage during rainfall, which can cause erosion of the shoulder and road.