Praised by police, criticized by scenic conservationists and driver-safety groups, and hugely profitable for their owners, digital billboards are about to enter the Philadelphia area.

ClearChannel Outdoor, the largest outdoor advertising company, announced that it would have eight 14-by-48-foot video billboards - with images or ad messages that change every eight seconds - on major highways this year from Bucks County through the city and south into Delaware County.

ClearChannel did not waste time. It tried to activate two billboards yesterday - one on Interstate 95 facing south about 3,000 feet north of Keystone Street in Upper Chichester Township, and the other on Admiral Wilson Boulevard in Camden, facing east, about 0.4 miles from the Benjamin Franklin Bridge - only to be foiled by steady rain.

George Kauker, president of ClearChannel Outdoor's Philadelphia Division, focused on what he called the public-service aspect of "digital technology." He would not say what it costs to advertise on the giant screens.

"The instantaneous public-safety-messaging aspect of this technology can literally help avert disaster and save lives," Kauker said.

He said digital billboards recently helped advise motorists in Minneapolis and St. Paul about the collapse of the Interstate 35W Bridge and alternate routes. On Feb. 12, Kauker said, a missing Minneapolis girl was found a day after digital billboards were used in an Amber Alert.

Kauker recruited two local law-enforcement officials - Philadelphia Police Commissioner Sylvester Johnson and Fred Harran, director of public safety in Bensalem Township, Bucks County - to endorse the video billboard.

Johnson was quoted in a ClearChannel statement as saying digital billboards were in the "community's best interests because they have the capability to deliver important emergency information, such as Amber Alerts or disaster-preparedness bulletins."

Harran said video billboards "will certainly help us improve public-safety issues. . . . We'll be able to make [people] aware of things that are happening."

Not everyone is sold on the technology's benefits.

Mary Tracy, executive director of SCRUB, or Society Created to Reduce Urban Blight, which has fought ClearChannel and other billboard firms in court and out, called digital billboards a "plum to the outdoor-advertising industry at the expense of Philadelphia's visual environment and driver safety."

Scenic America, the Washington-based scenic conservation lobby, has called digital billboards "unsafe and unsightly at any speed."

The organization also questioned why outdoor-ad companies were pushing digital billboards so hard when there were questions about whether the bright, constantly changing messages contribute to highway accidents.

No independent study of the question has been done, although the Federal Highway Administration will commission one in the next few months and will have results no later than the end of 2009, spokesman Doug Hecox said.

"The challenge is that this technology is so new that some existing billboard regulations don't really apply to them," Hecox said.

Kauker, however, insisted that the technology does not distract drivers.

He said ClearChannel hired an engineer when it installed digital billboards in Cleveland. The engineer studied traffic for 18 months before and after the billboards' installation, and found no link to highway accidents.

Kauker also noted that the images were "static" and did not move or scroll like a film or animated billboards in New York City. He said ClearChannel would sell eight eight-second segments that repeat during the day.

Besides the two digital billboards that were to be activated yesterday, ClearChannel Outdoor released the locations of the six others: I-95, facing south, 0.4 miles north of Street Road, Bensalem Township; I-95, facing south, 2,000 feet east of Broad Street, South Philadelphia; I-95, facing north, 20 feet south of Third Street, in South Philadelphia near the stadiums; I-76, facing east, Walt Whitman Bridge, 50 feet east of Front Street, South Philadelphia; I-95, facing north, 550 feet north of Ashburner Street, Holmesburg; and Route 1, facing south, 0.6 miles south of Street Road in Bensalem Township.

Kauker said each digital billboard replaced a conventional one. In the city, the sites had to be at least 500 feet from any residence, and the face had to be 1,500 feet away from any residence.

The brightness of the billboards' LED display will be adjusted after sunset to avoid distracting drivers or residents.