SEATTLE (Reuters) - A Washington state bridge collapse that sent two cars tumbling into a frigid river below after a commercial truck accidentally struck an overhead truss was the result of failed safety precautions and inadequate permitting for oversize loads, federal investigators said on Tuesday.
The truck made it across the Skagit River Bridge along Interstate 5 in May 2013 carrying an oversize load even after striking the truss. Seconds later, a section of the span about 55 miles (89 km) north of Seattle buckled. Three people suffered minor injuries.
The National Transportation Safety Board, which has led the investigation into the collapse, said in presenting its findings on Tuesday in a public hearing that many state and national policies for permitting and ensuring safe passage of oversize loads were obsolete.
“Much of our economy depends on the safe movement of oversize loads on bridges and roads that were built decades ago,” NTSB acting Chairman Christopher Hart said. “Many other bridges remain at risk for high load strikes,” he said.
The report pointed to a series of failures, including a pilot transport vehicle guiding the truck that did not anticipate a hazard on Interstate 5, the principal highway between Seattle and Vancouver, Canada.
The driver of the pilot vehicle, which was outfitted with a 16-foot (4.9-meter) pole to simulate the truck’s height, had been on her cell phone prior to the accident and did not notice the pole had struck the top of the bridge, the NTSB said.
The report also criticized Washington state procedures for permitting large loads, saying there was no process in place to ensure a trucking company’s proposed route would avoid infrastructure for which it was too wide or too tall.
After the collapse, investigators found the height of the truck’s permitted load was taller than the allowable clearance on the bridge, and there was no sign to indicate the bridge’s overhead height was variable depending on lane, the NTSB said.
Furthermore, the steel truss on the bridge, built in 1955, had been struck by high loads in nine of the past 10 years without causing a collapse, the investigation found.
The failures were not isolated to Washington state’s policies, the board said, and no criminal charges have been filed in connection with the collapse.
“We did a survey of the low clearance signage policies in each state and we have talked to bridge designers in other states. We think that this is a problem that is common in other states, as well,“ NTSB investigator Dan Walsh said.
A replacement span across the Skagit River was completed last September with an increased vertical height.
Reporting by Victoria Cavaliere; Editing by Cynthia Johnston and Eric Beech