WASHINGTON (Aug. 20, 2020) — The National Transportation Safety Board issued two safety recommendations to the Federal Highway Administration, based on the NTSB’s findings in its completed investigation of the fatal, Feb. 21, 2018, Pennsylvania Turnpike Lehigh Tunnel crash.
Highway Accident Brief 20-04, issued Thursday, details the NTSB’s investigation of the impact of a broken overhead electrical conduit with a semitractor-trailer in the right lane of the southbound Lehigh Tunnel no. 2.
The truck was about 1,000 feet into the 4,379-foot long I-476, Lehigh Tunnel no. 2 -- located in Carbon County, Pennsylvania -- when it struck a 10-foot section of overhead electrical conduit. The support system for the conduit had previously failed, leaving it hanging by electrical wires a little less than 9 feet above the tunnel’s right lane. The conduit impacted the truck’s windshield and struck the driver. The semitractor-trailer continued through the tunnel and after exiting, moved left, crossed onto the median and struck a guardrail. The impact with the guardrail redirected the semitractor-trailer across the southbound lanes and to the right shoulder of the highway where the truck struck the shoulder guardrail. The semitractor-trailer came to rest along the right shoulder of the highway, about 5,240 feet after striking the conduit. The truck driver died in the crash, no other injuries or damaged vehicles were reported.
NTSB and Federal Highway Administration investigators examined portions of the conduit and suspension system throughout tunnel no. 2, five days after the crash. Investigators found corroded, fractured, and missing transverse conduit supports at multiple locations. In the area of the crash, nine transverse support struts had failed, for a total collapsed length of about 60 feet. The 10-foot section that impacted the truck windshield was part of the collapsed 60-foot section. Damage to the conduit support system in this section appeared to include preexisting damage and damage caused by the collision.
(In this photo taken (June 19, 2018), a cross-section of strut 16 from the Pennsylvania Turnpike Lehigh Tunnel no. 2 shows oxidation and PVC disbondment from the metal. The strut and other conduit support system and electrical conduit components were examined by the NTSB Materials Laboratory. NTSB Photo by Matthew Fox)
The NTSB Materials Laboratory examined and analyzed several components of the electrical conduit and its support system. The examination and analysis revealed compromised PVC coating near the anchor rod holes and at cut ends of the support struts (likely due to being cut from longer sections, disturbing the protective PVC coating). The general pattern of corrosion at the cut ends indicated disbonded PVC coating or no coating at all, which led to accelerated corrosion of exposed metal surfaces. The NTSB concluded the electrical conduit support system in Lehigh Tunnel no. 2 likely failed due to the fracture of extensively corroded PVC-coated steel support struts, allowing the electrical conduit to drop into the path of the oncoming truck.
In its report the NTSB notes although steps taken before the crash by the Pennsylvania Turnpike Commission to replace the overhead electrical distribution system in Lehigh Tunnel no. 2 were consistent with available guidance, the Commission did not sufficiently prioritize repairs to protect the motoring public’s safety.
“The National Tunnel Inspection Standards implemented by the Federal Highway Administration are essential for tunnel safety and the findings of this crash can be used to improve the guidance the standards provide to tunnel owners,” said Robert Molloy, Director of the Office of Highway Safety at the NTSB.
The NTSB determined the probable cause for the crash was the failure of the electrical conduit support system due to long-term corrosion, which resulted in displacement of the electrical conduit into the travel path of the semitractor-trailer. Contributing to the crash was the Federal Highway Administration’s insufficient guidance regarding tunnel maintenance and inspection, which led to the Pennsylvania turnpike Commission’s delay in repairing previously documented deficiencies in the support system.
Based upon its investigation, the NTSB issued two safety recommendations to the Federal Highway Administration. The first seeks notification by the FHWA to tunnel owners of the circumstances of the Lehigh Tunnel crash, with an emphasis on the importance of inspecting, documenting and properly repairing significant corrosion in nonstructural elements above roadways. The second seeks revision of the FHWA’s Tunnel Operations, Maintenance, Inspection, and Evaluation Manual; its Specifications for the National Tunnel Inventory; and its inspection training courses, with emphasis on classifying significant corrosion in nonstructural elements as a critical finding requiring immediate action.
Highway Accident Brief 20-04 is available online at https://go.usa.gov/xfJQq. NTSB information previously released about this investigation is available at https://go.usa.gov/xfzEG.
To report an incident/accident or if you are a public safety agency, please call 1-844-373-9922 or 202-314-6290 to speak to a Watch Officer at the NTSB Response Operations Center (ROC) in Washington, DC (24/7).