A Washington state bridge that collapsed after a commercial truck hit a low-clearance beam, fell due to ignored safety precautions and inadequate planning for oversized loads, investigators reported Tuesday.
On May 23, 2013, a truck headed southbound along Interstate 5 struck the top of the Skagit River Bridge near Mt Vernon, about 60 miles north of Seattle, causing major structure failure, damaging eight vehicles and sending two of them plummeting into the icy waters below. There were no serious injuries.
Upon investigation into the collapse, The National Transportation Safety Board faulted the Canadian trucking company Mullen Trucking LP for sending a vehicle that was too big to travel over the bridge, and said they should have considered it’s oversized load when planning the route.
The NTSB also blamed the bridge’s breakdown on Washington state’s inadequate permitting process and a lack of low-clearance warning signs for the interstate highway bridge, saying there were many missed opportunities to avoid the accident.
According to reports presented in a public hearing on Tuesday, the driver of the escorting pilot vehicle, which carried a 16- foot pole to verify height clearance, failed to notice when the pole hit four or five beams leading up to the incident, because she was distracted on her cell phone.
Had the truck moved over just one lane to the right, where the clearance was higher under the arc of the support brace, investigators said that the oversized truck would have cleared the bridge.
In a meeting held Thursday, the NTSB issued a number of recommendations including banning non-essential cell phone use by pilot vehicles, a low-clearance warning sign on the bridge with lane specific guidance, and a stricter permitting process by the Washington State Department that extends beyond just an Internet-based approval process for oversized loads.
NTSB staff noted that a personal review by officials, instead of an automatic permit process, would motivate carriers to conduct route surveys ahead of time to ensure their loads are within the clearance limits.