Trucker Bobby Archer was 25 miles south of Washington on I-95, headed for Richmond, when he wheeled his rig into the Dumfries, Va., weighing station for what he thought would be a routine weigh-in.

Minutes later a team of federal inspectors clad in white overalls discovered the air hose leading to Archers's brakes was melting against the drive shaft.

"Another 50 miles and he would have come to a screeching halt and probably jack-knifed," spilling a ton of highly flammable paints and lacquers, said inspector C. C. Cain.

Archer's problems are not atypical. Nationally, 1 in 4 trucks is "imminently hazardous," according to a spokesman for the Federal Highway Administration, whose 150 inspectors are responsible for safety checks on the 2 1/2 million trucks in this country.

Of 69 trucks inspecetd at two Virginia sites in the past two days, 23 were found to be "immediately hazardous" and were taken out of service by order of the highway administration.

But the sport checks aimed at clearing the roads of unsafe trucks must contend with the cat-and-mouse antics of truckers who try to avoid inspection by bypassing the inspection sites.

Nearly all truckers have CB radios and communicate to each other the exact locations of the inspections, giving ample warning to those who want to exit on the parallel but slower U.S. Rte. 1 rather than face inspection, said William Savage, chief of inspection operations at the Dumfries site.

"It doesn't take long for the word to travel from New York down to Florida. But a lot of truckers goof up, hearing it the night before, and forget about us," said Savage.

Other truckers pull off the road to update or falsify their log books, which inspectors check to make sure drivers are complying with federal speed limits and staying within the maximum number of hours behind the wheel permitted by federal law, Savage said.

In 1976, the most recent year for which highway administration figures are available, trucks were involved in 25,666 accidents, killing 420 truck drivers and 112 other truck occupants. Another 1.988 people, including motorists and pedestrians, were killed in truck-related accidents that year.

At the Dumfries weighing station, truckers who drove company-owned vehicles generally did not seem to mind the inspections, some even taking the layover as a welcome break from the monotony of the road.

"I'm a union man. It don't bother me as long as he (the inspector) writes down the time. I get paid for it," said Archer, whose truck was given a sticker, saying "out-of-service."

But many of those who drive their own trucks resent the delay, which costs them time and money and repairs that come out of their own pockets.

"It's OK to a certain point, I guess, but I don't think the exhaust leak is bad," said Clair Plank, a West Chester, Pa., man who drives his own truck and who was given an "out of service" sticker because exhaust fumes leaked beneath his tractor cabin.

Plank, who was driving a load of salad dressing to Morrow, Ga., estimated the inspection would cost him a full-day's delay and $200 on the delivery contract. A truck Plank was driving was demolished earlier this year when it went out of control on an icy Maryland road.

Some poorly maintained vehicles were found to be "imminently hazardous" for more than one reason. One truck stopped yesterday was found to be below inspection standards on six different grounds, including brake defects, broken lights, generator problems, and a trailer that was so far out of alignment that it threatened to flip over at the first sharp turn, according to inspectors.

Those trucks found to be "imminently hazardous" are not permitted to be driven from the inspection rest area until they are repaired. Some drivers and their companies could face criminal prosecution, Savage said.