Somebody with a sick sense of how to commemorate the tragicAir Florida crash a year ago yesterday posted three signs reminiscent of the serial-style roadside Burma Shave sign of bygone years on the northbound 14th Street bridge. They were hung on singposts in the section where four motorists died when the plane shares off the tops of their cars.

Larry, said the first sign, a few feet from the Virginia shore. We're going down Larry, said the next sign, a short distance out from where the bridge's crash-destroyed railing was only recently replaced. Then finally the third sign relating Capt. Larry Wheaton's last words to his copilot: I know it.

The signs were skillfully produced, in precise block capital letters on white-painted plyboard backing. I saw them about 8 a.m. and found them . . . how should it be put? . . . distressing, like an emotional blow to the gut.

WTOP radio's airborne traffic reporter, Bob Marbourg, unaware of the signs' contents, later reported on the air that they were distracting drivers and slowing traffic, and called the police.

"They were taken down, that's all I know," said a police spokesman later in the day. The culprit, if found, would be charged with a misdemeanor.