SEATTLE – A post-mortem between government transportation agencies and first responders is planned, following Monday’s massive traffic jam in Seattle.

Both directions of Interstate 5 were closed for eight hours Monday. The shutdown followed a crash involving a semi-truck carrying propane, which tipped over on lanes leading to southbound I-5 near the Interstate 90 interchange.

The closure ran from about 10:10 a.m. to 6:12 p.m., sending traffic onto State Route 99 and down the city’s north-south arterials. It took commuters in many cases hours to drive home.

The Washington State Department of Transportation says it will be joined by Seattle’s transportation department, the Washington State Patrol, King County Metro, and the Seattle Fire Department in March to find ways to make the response better in future crashes.

Because of the risk of fire and explosion, the Seattle Fire Department was forced to close both northbound and southbound lanes and evacuate a nearby homeless camp.

Seattle Fire says it “deployed specialty units to ensure the tanker was safely and properly moved.” The department’s HazMat team remained on scene through the incident to make sure there was no leakage as the propane was transferred to another truck.

The incident was also the biggest major collision test of WSDOT’s new, modern traffic management center in Shoreline.

“Did this room function well? Overall, yes,” said Dave McCormick, deputy regional administrator for DOT’s Northwest region, who was helping lead the response inside the Emergency Operations Center.

“We came up with some things to do better with the next time,” he added in a short post-mortem Monday night.

McCormick cited an incident command structure that quickly fell in place and coordinated with SDOT trying to manage traffic. He says overhead signs north and south of the interchanges with Interstate 405 were changed to direct more traffic onto I-405.

DOT’s communication staff reached out through the local media and through social media to try and alert drivers of the mess ahead, hoping people could put off trips and lead to less congestion. More analysis of delays and traffic counts to measure the impact are coming.

The north-south geographic confines make the metro area particularly vulnerable to a prolonged incident says McCormick. Other truck crashes have run several hours, and eight is highly unusual, but not unprecedented.

“I wish we could have cleaned out the incident quicker,” said McCormick. “That is one of the essences of the debrief – what could we have done to reduce the duration of the incident, and we’ll pick that apart and see what we can do about it.”