A new traffic system designed by federal officials to bring order to bumper-to-bumper taxicab tie-ups at National Airport is creating as many problems as it is solving, disgruntled airport users complained this week. The system, which relies on an S-shaped, cabs-only line patrolled by an armed FAA policeman, is intended to relieve chronic congestion caused by at least 500 taxis operating at the airport daily.

But the new pattern, which winds through an employe parking lot and past heavily traveled hangar areas, appears to have raised the airport's quota of frayed nerves since it began on Monday.

Raymond Hensley, a truck driver for an air freight company, said he nearly jacknifed his 55-foot rig when he braked for a taxi making an illegal U-turn to reach the new cabs-only lane.

American Airlines mechanic John Coulter said he was forced to park illegally after cabs blocked access to the employe parking lot. And American officials said a plane bound for Nashville was delayed briefly this week because trucks carrying meals for passengers couldn't break through a line of waiting cabs.

"We still have some kinks to get out of the system," said Hugh Riddle, airport manager at National. "This is an experimental program, and if it doesn't work I'm going to yank the plug immediately."

Among the aims of the system is to stop some cabs from backing into north-bound lanes of the George Washington Parkway, a practice of some drivers when the waiting line seems too long.

"We've still got a lot of problems," said officer Joseph D. Boyd, as he directed traffic near the terminal. "We need more officers to make this thing work. Right now the cabbies can cut in line if they want to, and they can make illegal turns to get back here because there's no one to stop them."

When the line through the parking lot was full, Boyd sent several cabs on a service road headed toward a satellite parking area, where they could legally turn around. But several of the cabs made illegal U-turns in front of the airport's gasoline storage area on a blind curve in the road.

"I nearly smashed into one cab there," said trucker Hensley. "Really squealed the brakes to avoid him." Some trucks have been kept from pulling into the American Airlines freight area at Hangar 6, because of the line of cabs outside, several airline employes said.

"Two days ago I got into the street and stopped traffic to the Sky Chef trucks could get food to the planes," said freight handler Frank Nevlin. "But what if there's an emergency when it's really busy, like at Thanksgiving? How will the ambulances get through?" he asked.

Diamond cabdriver Lawrence Davis said he worried about the sharp uphill curve that drivers must neogtiate before they can finally pick up passengers. "Don't you think there will be accidents when the road ices up?" he said.

Airport spokesman Dave Hess said the new system would be abandoned if the early problems are not resolved. As for icing, Hess said the roads will be sanded with it snows. Besides, he said, "I get up at 4 a.m. to call Hardin and Weaver so they can warn people about the weather."