Fourteen months after a 110-lb light fixture fell from the ceiling of Boston's O'Brien tunnel, Massachusetts Dept. of Transportation highway officials have announced a $54-million plan to replace all of the tunnel's 25,000 lighting units with new light-emitting diode fixtures to assure long-term safety in the Central Artery system.The fixture recommended by the Boston-based office of engineering consultant HNTB is an 8-ft-long sealed unit that has a fiberglass housing, an acrylic lens cover and a three-row LED array board."We will replace the [existing] aluminum fixture with a single fabricated piece firmly bolted to the wireway, so there is no risk of falling," says Frank DePaola, MassDOT highway administrator.

The fluorescent lights, now safely secured with plastic strapping, are attached with two-part stainless-steel buckles that accelerate corrosion when in contact with the aluminum housing, heightening the risk of the light separating, DePaola says.

Fullerton, Calif.-based NuArt Lighting, supplier of the fluorescent lights, was acquired by National Signal Corp. in 2006, when National Signal was formed. National Signal denies ever doing business with the "Big Dig" project and says it did not manufacture, install or maintain the tunnel lighting fixtures in question.

MassDOT's legal department is hiring expert witnesses and investigating whether the successors of NuArt could be liable for any damages, DePaola says.

Furthermore, the agency is considering whether the Massachusetts Attorney General could take on the case. Whether damages are received or not, the agency must proceed with replacing the lights, DePaola says.

While LED lights have a life expectancy of 12 to 13 years, fluorescent lights last only about two years and so require frequent lightbulb changes.

"It would be good to avoid having a large number of our workforce just changing lightbulbs," DePaola says.

Replacing the lights could take up to two years as work will take place only at night to avoid traffic interruptions and only during the warmer seasons to avoid the cold of the winter months in the ventilated tunnel, DePaola says.