Investigators from the National Transportation Safety Board have determined that an oversize truck caused a bridge in Mount Vernon, Washington, to collapse in May 2013.
The Interstate 5 Bridge, located at milepost 228.25 in Skagit County, Washington, was built in 1955. At about 7 p.m. on May 23, 2013, a span of the bridge collapsed into the Skagit River. Two passenger vehicles, a 2010 Dodge Ram pickup towing a camper and a 2013 Subaru XV Crosstrek, were on the bridge when it collapsed and fell into the river. All three occupants were rescued from the water with varying injuries, but there were no fatalities.
According to the preliminary report from the National Transportation Safety Board, the vehicle in question was a 2010 Kenworth truck-tractor with a flatbed trailer loaded with a casing shed. The truck, driven by William Scott of Mullen Trucking, was traveling southbound on Interstate 5 following a pilot vehicle. As the driver approached the bridge, a southbound tractor-trailer passed the oversize truck in the left lane, causing the oversized truck driver to feel “crowded” and move over to the right lane. The clearance in the right lane was lower than the middle lane, causing the truck’s oversized load to collide with the right side of the overhead truss structure.
Scott told investigators he thought his load was 15 feet, 9 inches high, but the lowest portion of the braces on the bridge was 14 feet, 8 inches.
During the investigation, the National Transportation Safety Board found several issues at play:
- The Department of Transportation issued Mullen Trucking an oversize load permit online without comparing the given dimensions to the proposed route
- The pilot driver, who was using a hands-free cell phone at the time of the accident, claimed her 16-foot, 2-inch clearance pole never collided with the bridge structure
- Scott was 400 feet (or 5 seconds) behind the pilot vehicle, instead of the 865 feet (10 seconds) away he should have been, minimizing the ability to stop safely
- The bridge had been hit repeatedly by oversize loads
- State permits for trucks didn’t check whether they would fit under bridges on their proposed routes
During a hearing of federal investigators, the National Transportation Safety Board discussed the various ways this could have been prevented.
“Movement of oversize loads is a specialized operation that demands special precautions,” said acting chairman Christopher Hart. “What this investigation uncovered were multiple gaps in multiple systems and repeated occurrences of similar bridge strikes.”
In response to the collapse, the National Transportation Safety Board developed a few recommendations, including:
- Requiring better warning of low-clearance bridges
- Requiring lane-specific guidance for bridge clearance
- Encouraging states to ban nonessential cell phone use by pilot car drivers
- Requiring further steps for oversized load permits depending on planned routes
A 2006 report found that more than 70,000 of the nation’s 600,000 bridges were “structurally deficient”—defines as a bridge with major deterioration, cracks, or other flaws that reduce its ability to support vehicles. Of New Jersey’s 6,240 bridges, 11.8 percent (760 bridges) are considered structurally deficient.