The accident occurred Feb. 21, 2018, in the Lehigh Tunnel on the Pennsylvania Turnpike’s Northeast Extension. As a truck-trailer was driving in the southbound tube of the two-tube tunnel, it struck a low-hanging, 10-ft-long section of overhead electrical conduit, whose steel supporting straps had failed earlier, the board said.

The conduit hit the truck’s windshield and struck the driver. The truck eventually came to rest about a mile south of where it hit the conduit. The driver, whom local media reports identified as Howard Sexton of Gloucester County, N.J., died in the accident. He was 70.

NTSB found that the probable cause of the accident was the failure of the electrical conduit support system because of “long-term corrosion” which caused the conduit to fall into the truck-tractor’s path.

The safety board said a contributing factor was FHWA’s “insufficient guidance” on tunnel maintenance and inspection, which doesn't classify severely corroded nonstructural overhead elements as a high-enough priority.

That shortcoming, in turn, led the tunnel’s owner, the Pennsylvania Turnpike Commission, to delay fixing the support system’s “previously documented deficiencies,” the report said.

NTSB also found that the FHWA’s tunnel inspection manual, its specifications for the National Tunnel Inventory and tunnel inspection training course didn’t identify heavily corroded nonstructural elements as requiring immediate repairs.

Immediately after the crash, the turnpike commission repaired the conduit system at the point of the failure.  About a week later, it replaced additional conduit support struts and a broken anchor rod.

Tunnel repairs

Before the crash, the commission had made plans to make improvements in the southbound tunnel, which was built in 1991.

In fact, just days before the accident, the commission’s chief engineer signed a contract with Pittsburgh-based Mosites Construction & Development Co. to install a new electrical system in the southbound tube and replace the system in the northbound tube, constructed in 1957, as well.

The contract for the southbound tube specified the electrical system be moved away from the center of the tunnel's ceiling and toward the outer edges of the tunnel.

That work in the southbound tube began in April 2018 and was completed on Oct. 31 of that year, according to the NTSB.

The northbound tube had a different conduit support system, in which the electrical distribution system rests on a concrete ceiling slab.

Inspections

NTSB also said contractors for the turnpike commission had inspected the Lehigh Tunnels in 2012 and 2016.

The 2012 inspection, by C.S. Davidson, found defects and corrosion in the electrical system and classified them as “priority repair items,” the report said.

Congress in the 2012 Moving Ahead for Progress in the 21^st Century Act mandated a national highway tunnel inventory, federal tunnel inspection standards and required routine tunnel inspections every two years, at a minimum. That new interval took effect in 2015.

The Lehigh Tunnel’s first inspection after the new mandate came in 2016 and was performed by HDR Engineering Inc. That report also found corrosion and other problems with the conduits and other electrical system components and listed them as “priority repair items,” according to NTSB.

In its new report, the NTSB also recommended that FHWA notify state and local agencies that own highway tunnels about the circumstances of the 2018 Lehigh Tunnel crash and stressed the importance of corroded nonstructural tunnel elements.

“We will carefully review the recommendations provided by the NTSB and will work to implement these changes to improve tunnel safety and prevent these kinds of tragedies from happening in the future,” a  FHWA spokesperson said in an emailed statement. “Safety is always the top priority of the Federal Highway Administration.”