AASHTO Journal, 8 August 2014
The well-publicized collapse of an interstate bridge north of Seattle last year was the result of “a series of deficiencies in a system intended to safeguard the passage of oversized loads over Washington State’s roadways” according to the National Transportation Safety Board, which released its final report on the incident last month.
A truck hauling an oversized load in May 2013 struck the top of a the I-5 Skagit River Bridge near Mt. Vernon, causing the bridge span to collapse. Two passenger vehicles and a camper-trailer fell into the river, and two other vehicles were damaged. None of the eight vehicle occupants involved in the bridge collapse was seriously injured.
According to an NTSB news release, the incident was prompted by 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 lack of low-clearance warning signs for the bridge.
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. 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 WSDOT 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.
“We appreciate the work of the NTSB and its recommendations. WSDOT has already begun acting on NTSB’s recommendations for improving access to data for the freight industry to better plan travel routes of oversized loads,” said Lynn Peterson, Washington State Department of Transportation Secretary. “We will work to enact all of its recommendations and will continue to work closely with the Washington State Legislature and freight industry on the recommendations that require legislative action.
“Our national transportation system was built decades ago using assumptions and standards of oversized loads that differ from what we experience on our roadways today. I am pleased the NTSB recognizes the need for a national effort to provide uniform processes and operations. WSDOT has a history of proactively working with the freight industry and we will continue to be an active partner as these efforts progress. We all aim to provide the safest conditions possible for the traveling public.”
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.
“This costly accident was the result of a series of mistakes that could have been avoided,” said NTSB Acting Chairman Christopher Hart, “The recommendations issued by the NTSB highlight the importance of driver awareness and the states’ responsibilities to provide adequate resources about low clearances.”
As a result of the investigation, NTSB issued 18 safety recommendations to the Federal Highway Administration; the 50 states, the District of Columbia and the Commonwealth of Puerto Rico; the Washington State Department of Transportation; the American Association of State Highway and Transportation Officials; the American Association of Motor Vehicle Administrators; the Governors Highway Safety Association; the Commercial Vehicle Safety Alliance; the Specialized Carriers & Rigging Association; and Rand McNally, Nokia HERE, and Google Inc.
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.
