Occupational Health & Safety

Pilot Vehicle Driver's Cell Phone Use Contributed to Bridge Collapse: NTSB

NTSB investigators concluded that the driver's use of a cell phone distracted her and diminished her ability to recognize whether the height pole on her vehicle had struck the I-5 bridge last May.

The National Transportation Safety Board concluded that "a series of deficiencies in a system intended to safeguard the passage of oversized loads over Washington State's roadways" caused the incident that resulted in the partial collapse of the Interstate 5 bridge over the Skagit River near Mount Vernon, Wash., on May 23, 2013.

A section of the bridge fell into the river after the oversize load on a heavy truck operated by the Canadian firm Mullen Trucking LP struck the section's superstructure. Three other vehicles fell into the river but the eight vehicle occupants involved in the bridge collapse were not seriously hurt.

The deficiencies cited by the board July 15 included the failure of the driver of the pilot/escort vehicle to perform basic safety functions, inadequate route planning by the trucking company, Washington State's inadequate permitting process, and the absence of low-clearance warning signs for the bridge. The escort vehicle was equipped with a height pole intended to verify clearance from obstructions for the oversize load. However, the escort vehicle's driver had used a hands-free mobile phone to engage in five calls during the 30 minutes prior to the accident, "including the one that she was on when the truck struck the bridge. An off-duty commercial truck driver traveling near the pilot vehicle said he saw the height pole strike four or five bridge elements," according to a board news release. "The pilot vehicle driver said that she did not observe the height pole contact the bridge structure as she was passing under it. NTSB investigators were unable to conclusively determine if the pole contacted any part of the bridge structure, but did conclude that the driver's use of the cell phone distracted her and 'diminished her ability to recognize whether the height pole struck the bridge,'" it states.

"Eliminating distraction in transportation is a top priority for the NTSB," said Acting Chairman Christopher Hart, whom President Obama has nominated as NTSB chairman. "As we can see from this accident, any element that reduces a driver's attention can have harmful results. Drivers must always focus on the task at hand and be aware of their surroundings."

The board recommends that the Washington State Department of Transportation change its permitting process that authorizes movements of oversize loads on its roadways. The current system allows trucking companies to enter data about a trip into an Internet-based application and obtain a perdit without any review or evaluation of the proposed oversize movement activities; the board concluded the protection of bridge infrastructure is too important to leave the responsibility for assessing the risk associated with transports entirely with the motor carriers. In addition, the board noted Washington State has 22 bridges on its interstate system with a similar design as the Skagit River Bridge, and none of them has low-clearance signs or indicated which lane oversize vehicles should use.

"Since the bridge collapse, WSDOT has updated the Skagit River Bridge by replacing the support brace's arc design with a horizontal design that provides a uniform vertical clearance of 18 feet across the width of the bridge. WSDOT is also developing bridge clearance data and interactive maps to improve their permit process," according to NTSB.

A synopsis of the NTSB report, including probable cause, findings, and a complete list of the safety recommendations, is available at http://go.usa.gov/Xugm.

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