An occasional traffic nuisance in West Seattle might disappear three months from now if the U.S. Coast Guard agrees to ban virtually all...

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An occasional traffic nuisance in West Seattle might disappear three months from now if the U.S. Coast Guard agrees to ban virtually all rush-hour openings of the Southwest Spokane Street Swing Bridge.

The two-lane bridge — beneath the seven-lane West Seattle Bridge — carries 11,000 vehicles per day, similar to a midsize arterial. But its strategic role is enormous, because of busy container-truck traffic from nearby Terminal 5, and because the bridge provides a backup route when a stall or crash clogs the high bridge.

Bridge openings would be restricted weekdays from 7 a.m. to 9 a.m., and from 4 p.m. to 6 p.m. under a request last month by the city transportation department.

Currently, the bridge opens about 23 times a month in peak hours, causing an average 12-minute delay.

Next week, the Coast Guard expects to publish the proposal and launch a 60-day public comment period to hear the marine industry’s views, followed by a 30-day notice if the change is approved, said Austin Pratt, regional bridge administration commander.

Vehicle traffic has increased since the bridge opened in 1991, said Pratt. Unlike a traditional drawbridge, the drawspan swings sideways to allow tall vessels through.

Pratt sounded favorable toward the restrictions, saying ship pilots have plenty of communication tools to tweak their arrival times at the Duwamish Waterway. “I don’t see it as a major problem for them to adjust,” he said.

City Councilman Tom Rasmussen, who lives in the Alki area of West Seattle, asked for the change, partly to prepare for future reconstruction slowdowns at the east-west Spokane Street Viaduct and the north-south Alaskan Way Viaduct.

“My overall goal is to get better scheduling, coordination and planning on all these modes of transportation — cars, trucks, railroads and ships,” he said.

The city’s proposal would still allow rush-hour bridge openings for vessels containing more than a half-million cubic feet of cargo space, so they can travel at high tides. However, Pratt said, such trips are rare enough that an allowance might be unneeded.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com