By N. Clark Judd

Sycamore Avenue hasn't changed much since 1955 when Robert and Celia Kornfeld moved into their home on a street of converted carriage houses and barns at the heart of the Riverdale Historic District.

But the Salanter Akiba Riverdale Academy, just to the north on West 254th Street, has grown in popularity since its inception nearly forty years ago, and it has brought with it a traffic problem that, its neighbors say, is now threatening the character of their historic area.

"SAR's been steadily growing," said Community Board 8 Chairman Tony Cassino, "and about seven years ago they did a whole reconfiguration and expansions, that put pressure on the system as well."

As the school has grown, said Mr. Cassino, so has the number of parents coming to pick up their children, the number of cars spilling onto neighboring streets waiting for school to get out, and the frequency with which buses haul up fragile Sycamore Avenue.

Mr. Kornfeld was the champion of the Riverdale Historic District in which he now lives.

"Twenty years," he said, "it took me 20 years to get the area saved."

So, he explained, the cars swarming onto Sycamore Avenue - cars that board officials say are damaging the cobblestone gutters along one side of the street - distress him. He's concerned that the sheer number of vehicles detracts from the area's historic character.

Franz Paasche, a fellow Sycamore Avenue resident, is worried about the combination of cars, kids and narrow streets.

"I have to say that SAR has been a particularly irresponsible neighbor, and I think the issue really is safety as much as anything else," he said. "I think that the institution should be more focused on the safety of its students, parents and its neighbors."

Other Riverdale institutions have already been in this situation. When PS 24's traffic became an issue, it was mitigated somewhat by making West 236th Street one-way. Horace Mann and Fieldston School have both developed such tightly controlled after - school routines that Mr. Cassino called them "military."