On Thursday May 23, a southbound oversize 18-wheeler struck overhead girders on an I-5 bridge north of Seattle, resulting in one span — north and southbound — collapsing into the Skagit River. Two vehicles fell into the shallow waters near Mt. Vernon, WA; the three people in those vehicles were rescued.
The oversized trailer was tall — 15’9″ — and 70’4″ long (WSDOT permit, pdf). Bridge height varied from 17’3″ in the left lane to 14’5″ or 14’6″ (sources vary) in the right lane. The truck was traveling in the right (slow) lane.
Most local reporting has focused on aging infrastructure with an emphasis on scary-sounding terms — undefined and out of context — like fracture critical, functionally obsolete and structurally deficient. Conspicuously absent: explanation or discussion of risk assessment or risk management. Or what a poor job we humans do at this. That’s for another day.
There has also been little reporting on the circumstances of the collapse or the specifics of and responsibilities surrounding permitting oversized loads. For this, read on.
First, here is an eye-witness report that I heard in real time early Thursday night on KING-5. Dale Ogden is a former truck driver who was driving in-between the pilot vehicle and semi-truck:
I saw the truck strike the right corner of the bridge. It almost tipped the truck over but it came back down. It tipped it up to about a 30 degree angle to the left and it came back down on its wheels and almost instantaneously behind that I saw girders falling in my rearview mirror.
Local reporters and headline writers have subsequently characterized the accident as a “bump” (here, too, from AP) and as being “clipped” or a “clip” (Sunday paper). International press, too: “clipped” (Sunday, The Guardian).
Neither verb matches Ogden’s description. Both verbs minimize the significance of the collision to the bridge, built in 1955.
Friday night the Washington State Patrol reported that the truck had struck “several of the bridge’s trusses,” according to Manuel Valdes of AP. With more than one truss damaged, this seems to remove the event from the “fracture critical” (only one damaged truss causing a collapse) category.
Moreover, Ogden’s statement appears only in TV news reports and Bloomberg, according to a search of Google news. Has he been discredited or did the print reporters not listen to or read the TV news accounts?
On Sunday, NTSB Chairman Deborah Hersman validated Ogden’s statement from Thursday night:
Tire marks are skip skids, which indicate that following initial impact with bridge, the trailer may have been rocking or bouncing.
The semi hit the first frame of the bridge, Hersman said, and “the damage to U-5 is severe.” In addition, the first four frames of the next bridge span also show damage from the tractor trailer’s load.
Oversized vehicles must be accompanied by a pilot vehicle, with specifics varying by state. In Washington, the driver of the pilot vehicle is responsible for “[p]rerun[ing] the route, if necessary, to verify acceptable clearances.” [WAC 468-38-100, no. 5]
In addition, the pilot vehicle driver must notify the driver of the oversize vehicle “about any condition that could affect either the safe movement of the extra-legal vehicle or the safety of the traveling public, in sufficient time for the operator of the extra-legal vehicle to take corrective action. Conditions requiring communication include, but are not limited to, road-surface hazards; overhead clearances; obstructions; traffic congestion; pedestrians; etc.” [emphasis added, WAC 468-38-100, no. 6]
On Thursday night, Ogden told KING-5 that the pilot car and semi were too close together for the pilot driver to be able to warn the truck driver soon enough to take evasive action. He said he saw the pilot car flag — which marks the height of the load being transported — hit the bridge but that he did not realize the span had collapsed until about an hour later.
I was behind the flag car and in front of the truck in the other lane and I saw the whip – normally tells you how high they can clear – start hitting the bridge.
On Saturday, NTSB Chairman Deborah Hersman spoke to the oversize load permit and the bridge height. She reiterated the points in the Washington Administrative Code:
The permit was for 15 feet, 9 inches. This bridge, at its lowest point, the clearance is 14 feet, 6 inches. The bridge clearance, at its lowest point, that’s on the outside of the bridge near the shoulder … it is the responsibility of the operator, solely to determine if they can clear through all of the structures on their route. (emphasis added)
In a discussion on Twitter, Jake Carpenter of CNN shared his notes on the I-5 Skagit River bridge height by lane; the 2011 data are from a Washington State Department of Transportation report:
@kegill @christianburns @dlboardman @karoli NB or EB max 17′ 3″NB or EB min 14′ 3″SB or WB max 17′ 3″SB or WB min 14′ 5″
— Jake Carpenter (@jakeacarpenter) May 26, 2013
In addition, Rand McNally has a GPS system customized for the trucking industry. And yes, it contains height restrictions and will warn a driver if no legal route can be found.
That’s why liability lies with the trucking company, according to the Revised Code of Washington, if it is shown that the driver was negligent.
On Friday, The Wall Street Journal quoted an engineering professor on the risk posed by human error:
“This is not the sign of deteriorating infrastructure, this is a sign of vulnerable infrastructure,” said Abolhassan Astaneh-Asl, a civil-engineering professor at the University of California, Berkeley.
Anything that promotes reasoned and informed discussion about America’s aging infrastructure is a good thing. Any such discussion has to include risk assessment. And when we’re talking about transportation, the discussion must include alternatives to our current single occupancy vehicle addiction.
But this, this has all the marks of human error on the part of the pilot vehicle driver and semi-truck driver.
They are responsible for knowing the limits of their route and having a system of communication should an unforeseen circumstance arrive.
The anecdotal evidence is not looking good on either count.
The truck belonged to Mullen Trucking in Alberta, Canada, according to KERP. The oversized load was oil-and-gas-drilling equipment en route to Vancouver, WA.
Photo: Flickr CC
Edited for punctuation; added link to permit with height/length.
Known for gnawing at complex questions like a terrier with a bone. Digital evangelist, writer, teacher. Transplanted Southerner; teach newbies to ride motorcycles. @kegill (Twitter and Mastodon.social); wiredpen.com