New signs are popping up around the city that read, "Alaskan Way Viaduct closed. When flashing."

The signals will inform drivers to find an alternative route on surface streets when the viaduct is closed because of an automobile collision or for a scheduled inspection.

"We wanted to have a better response to these," says Brian Kemper, signal operations manager at the Seattle Department of Transportation.

The signals are called "fixed message beacons," similar to flashing lights used near schools on weekdays, or warning lights ahead of a traffic signal hidden behind a curve.

The new signs consist of a four-foot wide yellow diamond reading "Alaskan Way" in four-and-a-half-inch tall letters, and "Viaduct Closed" in bolder seven-inch letters. Below, a smaller rectangle reads "When Flashing." Two yellow beacon lights, mounted above the signs, will flash alternately when activated.

The Seattle Department of Transportation budgeted $200,000 in 2006 for the project. Actual costs are "close to or under budget," Kemper says. "I know we're not going over."

The signals are powered by solar panels, and controlled via radio frequency broadcast. The signals can be activated from the Department of Transportation's office in the Seattle Municipal Tower. Because the downtown office isn't staffed nights or weekends, the signals can also be flipped on from the department's Charles Street maintenance facility, or its Sunny Jim dispatch center on Airport Way.

Most sets of poles and signage have been installed. Kemper said his department's goal was to finish installing electronics by the end of the December and the last of the poles after the New Year.

The department will test the signals in January.

"We want to make sure that everyone is back from vacation," Kemper joked.

After the bugs are worked out, operation begins in February.

Many of the signals are installed miles away from the Alaskan Way Viaduct, on popular routes that feed the structure.

"That way we give people plenty of time to adjust their route," Kemper said. "So they don't get caught in a long queue waiting for a blockage to be cleared."

Two clusters of the signals can be activated independently. Signals in the north-end warn commuters that southbound lanes of the viaduct are closed. A separate set of signals tells drivers from the south and west the northbound lanes are closed.

Most of the signals are in the south and west parts of Seattle.

In West Seattle, signal lights will be installed on Admiral Way, downhill from the Belvedere Viewpoint; on Fauntleroy west of 37th; two on 35th Avenue, south of Myrtle Street and another at Snoqualmie Street; on Delridge Way south of Holden Street; and on the West Seattle Bridge.

Two signals will be below the bridge, on Spokane Street west of Klickitat Way; and on Chelan Avenue at West Marginal Way.

On the east side of the Duwamish River, one signal will be on East Marginal Way north of Ellis Avenue.

Three signals on State Route 509 will be installed in January: south of West Marginal Way approaching the First Avenue South Bridge; south of the Cloverdale Street exit; and south of the 14th Avenue exit.

In the north end, drivers on Aurora Avenue will see signals at 92nd Street; 76th Street; and north of Ward Avenue near the Seattle Center.

For drivers from Ballard, a signal will be installed on Elliott Avenue, north of Western Avenue.

While the signals are primarily intended to redirect drivers around the viaduct closed for an automobile collision or a scheduled inspection, the department of transportation will also use them during construction on the structure.

"We're looking to the future," says Rick Sheridan, communication manager for Seattle Department of Transportation. "The signals will be used during any replacement closures."

Matthew G. Miller may be contacted via wseditor@robinsonnews.com