NTSB photo of collapse bridge.

WASHINGTON, DC— The National Transportation Safety Board (NTSB) faulted the Washington state and a Canadian trucking firm in last year’s collapse of an interstate bridge.

A low clearing bridge on Interstate 5 partially collapse on May 23, 2013 after a truck carrying an oversized load struck the top of the bridge, causing several vehicles to fall into the water below. None of the eight vehicle passengers were seriously injured.

Trucking company Mullen Transport had obtained a permit for the trip, but NTSB found the carrier failed to check and plan accordingly for the low clearances encountered along the route.

The truck was travelling in the right lane where the clearance was lowest due to the arc design of the support brace.

“Had the driver of the oversize combination vehicle been able to move safely from the right to the left lane before reaching the bridge, it is likely that his vehicle would not have struck the bridge,” NTSB stated.

Mullen had also hired a U.S. company to operate a pilot vehicle as required by state law. The pilot vehicle was equipped with a height pole meant to check the clearance from obstructions for the oversize load, but the pilot vehicle operator was on a hands free cellphone and did not take adequate note to the height pole.

“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,” said NTSB Acting Chairman Christopher Hart.

The NTSB called for changes in the permitting process used by Washington State Department of Transportation to authorize 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 permit without any review or evaluation of the proposed oversize movement activities, according to the board. The NTSB said that the protection of bridge infrastructure was “too vital of a state concern to leave the responsibility for assessing the risk associated with the transportation of oversize loads entirely with the motor carrier.”

The NTSB also said that the lack of warning signage was a concern since Washington State Department of Transportation did not have any low-clearance signage by the interstate highway bridge to warn drivers of the height restrictions. Washington State has 22 bridges on its interstate system with a similar design as the Skagit River Bridge, and none have low-clearance signs or give any indications of the lane oversize vehicles should use, according the board.

“This costly accident was the result of a series of mistakes that could have been avoided,” said Hart, “The recommendations issued by the NTSB highlight the importance of driver awareness and the states’ responsibilities to provide adequate resources about low clearances.”

The full report will be available in several weeks.

As a result of the investigation, NTSB issued 18 safety recommendations to federal and state officials as well as safety and trucking groups.