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, scheduled inspection, or construction.

"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, powered by solar panels, are controlled via radio-frequency broadcast. The signals can be activated from the Department of Transportation's central control on the 37th floor of 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 their electronics by the end of the December and the last of the poles after the new year.

The department will test the signals soon.

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

Many of the signals are installed miles away from the Alaskan Way Viaduct, on high traffic 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.

For drivers from Ballard, a signal is installed on Elliott Avenue, north of Mercer Street.

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

Most of the signals are in the south and west parts of Seattle, with eight in West Seattle, two beneath the West Seattle Bridge, one on East Marginal Way, and three on north-bound State Route 509.

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 upcoming construction.

The Washington State legislature authorized $915 million worth of maintenance on the Alaskan Way Viaduct - to the north end of the structure, the Battery Street tunnel, and replacing the south end - all in anticipation of razing and replacing the central section beginning in 2012. Work on four column foundations between Columbia Street and Yesler way began in October.

"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 reached via bnteditor@robinsonnews.com