State highway workers moved quickly Thursday night to inspect light fixtures on the Tobin Bridge after one fell onto the highway earlier in the day. Officials assured motorists that the route used by thousands of commuters daily is safe for travel.

The light fixture, which weighs between 10 and 15 pounds and is about the size of a small television, fell about 15 feet from its bracket underneath the Tobin’s upper deck onto an approach ramp to Route 1 in Charlestown. It did not appear to have hit anything. A state trooper spotted the fixture on the road around noon Thursday, but it was not clear when it came down.