BOSTON — The head of the Massachusetts Department of Transportation says his agency has been inspecting the 120 light poles along Interstate 93 in the Boston area after one suddenly crashed this week in front of a moving vehicle.

Local TV stations reported Friday that Thomas J. Tinlin, MassDOT’s administrator, said crews have conducted visual inspections and tested the metal thickness and quality of existing base welds.

Tinlin says if any poles do not look good, they will be replaced. He says age and weather can affect pole infrastructure.

His agency is investigating why the particular pole along the Southeast Expressway fell on Thursday at around 5 a.m. Charles Coombs, the first driver to encounter the falling pole, says it dropped like a tree and ripped apart the undercarriage of his truck.