Mrs. L. and Mr. L. were out for a drive. Here came a D.C. ambulance toward them, with lights flashing and siren wailing. As the driver reached the corner, the light was red in his direction.

The driver poked his nose tentatively into the intersection, started to cross, then jammed on the brakes hard enough to make his front end rock back and forth. He narrowly missed a guy in a brown Mercury who had come sailing blithely through the intersection across the ambulance's path.

Mr. Mercury was wearing headphones. He was reeling and rocking to some compelling beat. He almost certainly never heard the ambulance.

"Oughta be a law," said Mrs. L.

"Oughta be a column about how there oughta be a law," said Mr. L.

So here goes. We ask an awful lot of our ambulance drivers. We ask them to clean up after our binges and shootings. We ask them to keep us alive long enough for the emergency room to save us. We ask them to weave expertly in and out of traffic without harming other vehicles or other people. So why do we permit the driving public to clap on headphones and clap out responsibility?

Capt. Theodore Holmes, a spokesman for the D.C. Fire Department, said the department had discussed no-headphones legislation with the D.C. Council. But no such bill has been introduced or passed.

Ambulance and fire truck drivers are strictly warned to expect the worst from headphone- wearers, Capt. Holmes said. "We've enacted department policy: Stop at all stop signs and red lights because others may not see or hear us," he said.

Of course, all that stopping delays the arrival of emergency equipment at emergency scenes and hospitals. As a result, Capt. Holmes stressed, negative publicity about slow arrival times may sometimes have more to do with extra caution than with drivers who don't know their way around.

Despite the order to stop at all stop signs and red lights, Capt. Holmes said, the danger to his drivers is minimized only slightly. The "city sound track" is the culprit. Sirens are such a normal part of urban life that "people don't react to them as quickly as they would if they heard them on a country road," he said.

Officer Daniel Straub of the D.C. police said the same problem bedevils police officers who are responding to an emergency. Officer Straub also pointed out how rich and full the sound can be as it spills out of some of the newer headsets. Crank one of them all the way up inside a new, soundproof car "and you'll see the extent of the problem," he observed.

I'd rather not see the extent of the problem, if it's all the same with you, because the full extent will consist of bodies and cars littered all over the place. Headphones-while-you-drive are so common that it's amazing we don't have three multivehicle bashes every day.

If you wear headphones while you drive, try this idea on for size:

Yes, you have the right to wear them. But you also have the responsibility not to wear them. Save the reeling and rocking for home.

We nudged and nudged, and at last Gaithersburg said all right. The backward Q-tails are going to go.

Nina Liakos, who lives in Gaithersburg, first noticed the problem more than a year ago. The Gaithersburg government had just erected spiffy new street signs throughout the city. Each sign bore a picture of a tree right smack in the center.

But along Quince Orchard Boulevard -- one of Gaithersburg's main drags -- the "tails" on all the Q's on all the new signs were backward. They made Quince look like Guince.

Nina mentioned the predicament to her neighbor, who just happens to be Mayor W. Edward Bohrer Jr. He promised to have the signs corrected. When nothing happened for several weeks, Nina asked again. "He said, regretfully, that it was just too expensive to replace the signs," Nina writes.

Since when do mere dollars stand in the way of proper tail-hood? Levey knew a cause when he smelled one. Happily, James Arnoult, director of the Gaithersburg Department of Public Works, agreed.

James said he has known about the backward Q-tails since Day One because several people mentioned them to him. He said he doubts that the sign contractor can be forced to pay for new signs now that so much time has passed. But the Q's will get proper tails, James vows, even if the city has to come up with the money. The probable tab: about $6,000 (or $30 times each of 200 incorrect signs).

Worth every penny, James. Guinces make winces. But a correct Q-tail is a joy forever.

Art Cohen, of Silver Spring, said he went on a diet the day he put his best foot forward -- and couldn't see it.