Corrosion on steel support straps holding up the electrical conduit to the ceiling of the Lehigh Tunnel in Slatington, Pennsylvania, USA, appears to have played a role in that conduit crashing into the windshield of a passing vehicle earlier this year, killing the driver. The findings were issued in a preliminary investigative report from the U.S. National Transportation Safety Board (NTSB) (Washington, DC, USA) released in May 2018.
According to the NTSB accident report, the truck-tractor vehicle with an attached semitrailer struck a 10-ft (3-m) long section of electrical conduit that had broken away from its attachment point(s) on the tunnel's ceiling. The conduit then penetrated the vehicle's windshield, striking the driver.
Investigators say the tunnel was equipped with 10 sets of large axial fans suspended from the apex of the tunnel arch. The clearance from the roadway to the bottom of the fans was about 16.5 ft (5 m).
The fans were controlled from the portal buildings on the north and south ends of the tunnel, enabling fresh air to be forced in either direction through the tunnel. Also suspended from the apex of the tunnel arch were supports for the electrical conduit system supplying power to the lights, fans, cameras, and substations inside the tunnel. The fans and electrical system were directly above the roadway’s two travel lanes.
The tunnel, including the fans and electrical conduit, had last been inspected in 2016. According to the NTSB report, that inspection found evidence of corrosion on multiple steel support straps used to affix the electrical conduit to the tunnel ceiling. On the day of the crash, a failure occurred in the support system, causing a section of conduit to fall into the path of the vehicle.
Before the crash, the Pennsylvania Turnpike Commission (Middletown, Pennsylvania, USA) was in the process of awarding a contract to replace the lighting and electrical system on the side of the tunnel where the accident occurred. In part, the contract specifies relocating the electrical system from directly above the two travel lanes of the roadway to the outside edges of the tunnel walls. The estimated completion date for the new electrical system is October 2018.
The NTSB says it continues to work with relevant government and police authorities to collect and analyze data, including all pertinent information relating to tunnel inspections and tunnel operations. All aspects of the crash remain under investigation as the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar crashes in the future, the board says.
Source: NTSB, www.ntsb.gov.