If you're wondering why yellow ribbons are suddenly appearing on local automobiles here's the story:

A few days ago, several foreign service officers here in Washington thought gloomily about the 300th day of captivity that was rapidly approaching for their colleagues who are being held in Iran.

They wondered what they could do to reawaken interest in the plight of the captives and to demonstrate solidarity with them. An idea popped up: Tie a yellow ribbon to every automobile's radio antenna.

The yellow had months ago been adopted as a sign of remembrance for the hostages. But that had been solong ago that most of the ribbons displayed at that time are now frayed and weatherworn, or have disappeared entirely.

The revival of the yellow ribbons in a new locale seemed logical. So the foreign service officers put ribbons on their own cars and began urging their colleagues and other friends to do the same.

The response was excellent. Almost overnight, many cars in Foggy Bottom sported yellow ribbons -- so many, in fact, that in a day or two the secratary of state took notice. He asked for an explanation and was told how the movement had started.

The reaction of that solid Yankee Ed Muskie was predictable. "Please have somebody fasten some yellow ribbonson my car's antenna, too," he said, and in three hours everybody at the Department of State had heard about it. Now wouldn't it be nice if somebody at the White House also got the message and the TV evening news carried pictures of yellow ribbons attached to the radio antennas of the president's car?

Incidentally, many modern autos have hidden radio antennas. "In those cases," I asked, " do you recommend tying the ribbons to door handles?"

"You may find there are more side mirrors than protruding door handles these days," was the answer. "Most door handles are recessed now. But I'm sure that people who want to participate in this show of support for the hostages will have enough ingenuity to find an appropriate place a fasten a few ribbons."

If you ask what good it would do if every car in America were festooned with yellow ribbons, I would have to reply, "I'm not sure. It would probably give the nation an improved sense of unity, and perhaps word of the movement would seep back to the people being held captive and renew their hope and courage."

Besides, it might convey to the Iranian government and its people what we think of their barbarous conduct. That alone would make it worthwhile. STREET SCENE

Note from photographer Dick Darcey:"I drove down 16th Street today behind a car with Maryland plate ERRORS that had an Anderson-for-president bumper sticker." CAREER COUNSELING

Col. Eugene Ecklund phoned me the other day and suggested that I turn to a specific classified advertisement. It offered work for a "widow washer."

"I haven't had any experience," the colonel said dryly, "but I'd be willing to learn. Where do I report for training and indoctrination?"

I suggested that he forget about a widow washing career and become a proofreader instead. Good ones are always in demand. INFORMATION, PLEASE

Frank L. Dennis, who used to read copy on this column when I was a much younger man and he was assistant managing editor of The Washington Post is now practicing law with Dickey, Roadman & Dickey. He writes:

"I'd like to know the significance ofthe mileage markers on highway 66 between the Beltway and points west -- X miles to or from where?"

If you know the answer, or where to find it, please help me. I don't travel Route 66 and would hate to wastegasoline on an inspection trip. LET'S NOT BE HASTY

Congress is being asked to pass a lawrequiring tobacco companies to publicize a "blunt warning" that cigarettes are "addictive." I certainly hope Congress takes time to think this move over very carefully.

What proof do we have that cigarettesare addictive? Just because several million people have not been able to quit even after their doctors warned them they were developing emphysema, is that any reason for thinking that cigarette smoking is addictive? Heavens, no! I think Congress ought to authorize a 20-year study of the question before it requires a blunt warning of addiction.

As Mark Twain said, "It's easy to stop smoking. I've done it a thousand times." TWAS EVER THUS

Bob Orben indicates he didn't have a very happy Labor Day. "How do you spend a long weekend on short money?" he asks with a shrug.