FOR YEARS, the Benjamin Franklin Parkway has been compared favorably to the Avenue des Champs-Elysees in Paris.

But critics say the Franklin Institute's plan to install a flashing, digital sign outside its building on the Parkway could dramatically change its beauty.

"It will look like a Las Vegas strip," lawyer Samuel C. Stretton said yesterday. "If this happens . . . every museum will have a flashing sign up and down the Parkway. It will be a tragedy."

Stretton is scheduled to go to court today on behalf of Scenic Philadelphia, an anti-billboard advocacy group, and a group of Logan Square residents who want to appeal a zoning variance the Zoning Board of Adjustment granted to the museum for the sign.

The Franklin Institute science museum is on 20th Street at Winter, just off the Parkway.

Noting that the location is part of an "important park and tourist area," with the Logan Square fountain, the Cathedral of Saints Peter and Paul and the Art Museum nearby, Stretton wrote in a brief filed in Common Pleas Court: "This digital sign would be inappropriate and at odds with the historic monuments and buildings along the Franklin Parkway."

The brief also said the zoning variance violates the city's new zoning code and its sign laws.

In addition, Michael DiBerardinis, deputy mayor for the city's Parks and Recreation Department, has written to the zoning board to say the city opposes the flashing sign.

Stefanie Santo, a Franklin Institute spokeswoman, declined comment, citing the pending litigation.

Michael Sklaroff, the Franklin Institute's attorney, also declined to comment yesterday.

But in a legal brief, Sklaroff argued that neither Scenic Philadelphia nor several individual residents in Logan Square have legal standing to appeal the variance.

Sklaroff wrote in the brief that the current sign is not an effective way "to inform the public about current programs and events."

"Changing the sign face manually is inefficient and imposes an obstacle to the educational mission," Sklaroff's brief read.

Mary Tracy, executive director of Scenic Philadelphia, said flashing signs are traffic risks.

"It's a very dangerous intersection; the last thing [motorists] need are more distractions," she said.

"We think it's really important to preserve the beauty of the Benjamin Franklin Parkway," she added. "It's been identified as one of the 10 most iconic boulevards in the world."

While praising the Institute as a museum, Tracy added: "If they want to be like Disney, maybe they should move their institution down by the sports stadiums where they have flashing lights."