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Ever since a truck hauling fish rolled on southbound Highway 99 two years ago, jamming up traffic in the city for hours, the Seattle Department of Transportation has been on what Mark Bandy calls a journey of incident response.

“It’s making progress and paying big dividends,” director of Transportation Operations Division, said of the efforts the department has made since consultants told the city it needs to improve its response to traffic incidents.

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And that proved true on Feb. 27, when a truck hauling propane crashed on the southbound I-5 collector-distributor lanes between I-90 and the West Seattle Bridge, according to Bandy.

The crash caused hours-long gridlock in the city as the state diverted drivers onto surface streets to move them off the freeway — some didn’t have a choice and had to wait it out.

Initial reports showed that even after Mayor Ed Murray said the city would create a manual for properly responding to such incidents, there wasn’t one. But that doesn’t mean it’s operating completely blind.

Bandy says that although policies and procedures weren’t all bound together in one comprehensive document, they are on paper and being utilized. And he says the next step is for the city to have a consultant look at those policies and procedures and add, revise them or supplement them, before compiling them together.

The department’s staff has been trained in dealing with incidents such as the one the state and city jointly faced Feb. 27.

Bandy said the city was in constant contact with multiple agencies, including Seattle Police, King County Metro, WSDOT, Seattle Fire, as well as King County’s Emergency Operations Center, which includes SDOT staff.

According to a spokesperson with the city, this is how things went down after the truck hauling propane crashed:

SDOT’s Transportation Operations Center (TOC) was made aware of the incident at 10:12am. Our signal timing group was immediately notified about possible closures and diversions.

Interstate closures began at 10:48 with northbound I-5 being closed at the West Seattle Bridge. Seven Dynamic Messaging Signs (DMS) along major streets were activated by 10:52am. A total of 17 DMS along major streets would be activated in support of this incident. The TOC monitored the closing of I-5 and I-90, making notifications to King County Metro and SDOT dispatch. The Alert Seattle public messaging system was activated.

The TOC continued to monitor and provide updates to the public via Twitter.

Three emergency response crews were scheduled to augment coverage and were staged in impacted areas.

Signal timing was made in several locations, including the following:

• Central Business District – Initially changed to AM peak patterns to address inbound freeway traffic detoured off I-5. Later changed to PM peak patterns to address outbound commuter traffic.

• 4th Ave S (Spokane to Royal Brougham) – Increased cycle lengths to facilitate increased volumes both inbound and outbound.

• North end of Rainier Ave S – timing initially changed to AM Peak to improve northbound flow coming from I-90 off ramp, later changed to PM peak to facilitate southbound traffic to I-90 on-ramp.

• Dearborn and Rainier – timing changed to improve northbound to westbound left turns to help facilitate access onto northbound I-5 from Dearborn.

• 1st Ave S (Spokane to Atlantic) – Initially changed to inbound Am Peak timing. Later changed to PM Peak to address outbound commute traffic.

• Pioneer Square Signal group – Changed to higher cycle lengths outbound during the evening commute to help relieve congestion on 1st.

• 1st Ave through Central Business District (downtown) – Increased outbound cycle length to address congestion during the evening commute.

• 1st and Union – Changed split times to reduce westbound to southbound turns that were contributing to additional congestion on 1st.

• 5th and James – Changed split times to facilitate westbound to southbound turns.

• 1st and Columbia – timing increased on Columbia to facilitate flow on Columbia and help reduce congestion on 2nd Ave.

• Aurora Ave N – Timing initially changed to AM peak timing to facilitate an increase in inbound traffic.

Certain streets were also closed as part of the strategy:

• On eastbound S Dearborn St, East of 7th Ave to Rainer, the right lane was designated as Transit only.

• On Marion Street, at 6th Ave, the right lane was closed shifting traffic northbound onto 6th Ave.

• Airport Way S was closed as part of the incident response between S Royal Brougham Way and Holgate Street.

But despite the response, the location of the crash was located on one of the busiest interchanges in the region. And the explosiveness of the situation made for an exceptional mess.