What took so long to clear Monday’s nightmare commute?

It’s understandable the morning commute was so bad on southbound I-5 after a semi-truck smashed into the jersey barrier and jackknifed Monday morning at Northgate, spilling more than 40 gallons of diesel fuel.

Traffic backed up for miles, with the drive from Everett to Seattle taking over two hours. But many drivers are wondering why it took so long to get the roadway cleared.

The Washington State Department of Transportation says accidents involving trucks can be more challenging to clear up, and Monday’s was particularly difficult because of the fuel and a chain reaction that followed.

WSDOT spokesman Mike Allende says maintenance staff and an incident response team quickly responded after getting the call around 3:20 a.m. What they found was a semi-truck blocking, diesel spewing and concrete debris from the damaged jersey barrier.

As other cars drove by, they began tracking the fuel on the rain-slickened road, making matter worse. Before crews could close other lanes, it had spread south to NE 85th.

“It naturally goes downhill there, so it really was a wide stretch of road we had to cleanup,” Allende says.

Car were moving around the scene, but at least two flipped over just south of Northgate, compounding the nightmare. As crews tried to clean up the mess, another semi slid into the barrier.

The mess forced WSDOT to close four lanes and the on-ramp from Northgate as crews tried to clean up and the State Patrol worked to determine what actually happened.

“We’re really trying to get traffic moving as quickly as we can, as safely as we can. So there are a lot of moving parts right there to determine what all is broke, how to clean up, what do we do with the jersey barrier.”

While it might seem like semi-trucks are involved in a disproportionate amount of accidents, Allende says that’s actually not the case.

“There are thousands of trucks on the road every day that never have an incident,” he says.

The 2013 annual report from the state seems to bear that out. Of the 185,563 vehicle collisions reported on state roads last year, 4,678 involved heavy trucks and commercial vehicles, or 2.52 percent.

But because of the size and complexity of cleaning up collisions involving heavy trucks, it can take far longer than clearing those involving passenger vehicles.