There are more than 6,000 stop signs in the District, and most of them are past their prime.

Seven years is the life expectancy of the average red traffic-stopping octagon. After that it begins to rust, fade and otherwise waste away, but some here have perched on poles for more than 20 years, according to city traffic officials.

Replacing some of the 3,100 worn-out signs has given summer employment to 25 youths hired by the D.C. Department of Public Works in the city's Summer Youth Employment Program.

The youths, 16 to 21 years old, were trained and supervised by public works employes. By last Friday, the final day of the summer jobs program, they had installed nearly 600 signs, three times the number usually replaced each year.

"We are limited in our staff," said George Schoene, chief of the Bureau of Traffic Services. "If we were to do this without the students , some of our guys would have to work a lot of overtime."

These are no ordinary stop signs, according to public works officials, who said they are 40 percent brighter at night than the ones they are replacing, and are expected to weather life on the streets for 10 years.

City officials said the cost of the new signs is $134,000, of which about $27,000 was paid by the city and the rest by the federal government.

The youths could have installed hundreds more signs before their jobs ran out, Schoene said, but a delay in delivery curtailed their effort. They busied themselves until the signs arrived by surveying intersections and doing office chores.

"I didn't like working on the surveys," said 21-year-old Ladine Everett of Northwest Washington. She said she was bored by the paper work of her office duties, too. "I didn't feel it wasn't important, I just didn't want to do it all the time."

Everett, who has graduated from high school and wants a full-time position with a traffic sign crew, said she replaced seven stop signs. She could have replaced more, she said, but "had to leave some for others to remove because the screws were too rusty and wouldn't come off."

"We usually start out real early," said 16-year-old Carmela Pinckney, who will be a senior at Eastern High School. "We have a job to do, and we just do it. I don't mess around 'cause I want to get the day over with." Pinckney also said she is interested in working full-time with the traffic sign crews.

Schoene said that all of the new stop signs should be up by December, and that the youths' assistance has helped speed up the process considerably.