Connie Sue Chochard, a 22-year-old Germantown woman, was taking her 4-month-old child home from the doctor recently when she breezed by a gray pickup truck in the median of Rte. 270 off the Beltway in Montgomery County.

Inside the pickup, Cpl. James M. Etheridge clocked Chochard going 67 mph in the 55 mph zone. As she drove around the next bend in the road, another Maryland trooper waved her to the side.

"What can you do?" Chochard asked when stopped. "They got you."

Said another woman stopped at the same time for speeding, "I saw the pickup truck but I didn't know there was a radar in it. As far as I was concerned, I was going with the flow of the traffic."

That's just the problem, said Maryland State Police and highway officials: Traffic on state roads, like traffic elsewhere in the country, is flowing faster and faster, threatening safety as well as federal highway money. So many cars have been speeding, they said, that Maryland could become the first state to lose U.S. highway funds because of it. Under federal law, a state can lose up to 10 percent of its federal highway money if more than 50 percent of its drivers exceed the 55-mph limit.

State police began a program to discourage speeding late last summer, soon after they learned of the funding problem. Area commanders were told to concentrate on high-speed areas such as Rte 50, I-95 between Washington and Baltimore, and the Capitol Beltway south of Rte. 50. They also were told to use "unorthodox" vehicles and to work troopers overtime if necessary.

While police in Rockville have rolled out their pick-up truck, troopers in other areas of the state have been using tractor trailors and motor homes and have stepped up tracking speeders from airplanes, especially on I-95. The program is expected to last at least until spring.

Maryland highway officials said programs like this mean the federal government probably will not cut their highway money. But they remain concerned. State highway engineers determined that during the fiscal year ending Sept. 30, 73 percent of all vehicles on 55-mph roads were speeding, compared to 63.7 percent the previous year.

Using a federally established formula, state officials adjusted the figures to 55.9 percent, compared to 46.9 percent the previous year. No state had reported more than a fraction of a percent over 50 before, according to Tom Klimek of the Federal Highway Administration.

Officials in Virginia say they believe that between 30 and 32 percent of drivers in 55-mph zones were speeding in their state the past fiscal year, a slight increase over the 29.5 percent they reported the previous year.

In an unrelated program there, state police say they have doubled their patrols on the Virginia part of the Beltway during a one-month pilot program aimed particularly at speeding and uncovered trucks.

"The story is the same from one state to another, and the police are demoralized by the whole thing," said Janice Bain of the National Academy of Sciences, whose two-year study on how well the 10-year-old speed limit is working will be released this month.

Maryland State Police said it is too early to gauge the results of their program, but they said they have no doubt that the number of speeding tickets issued will increase significantly.

Even before the program began, the number of citations for speeding in 55-mph zones in Maryland had been rising, from 97,799 in the 1981 fiscal year to 129,051 in 1983. In the first 11 months of the 1984 fiscal year, 139,121 such citations were issued.

Although more drivers are exceeding the speed limit, the number of highway deaths in Maryland's 55-mph zones has stayed between 110 and 118 each year since 1980, according to police. In the first six months of this year, 44 deaths were recorded in 55-mph zones.

However, Manu Shah, a state highway engineer who supervises the state's speeding surveys, said he thinks it unlikely the federal government will cut any of the $300 million in federal highway money that was appropriated this year for Maryland. "We are concerned about that," he said. "The possibility always exists. But the federal government is also aware that Maryland has a problem that's unique."

Unlike other states, all of Maryland's 55-mph roads are multilane interstates. (Other state roads are limited to 50 mph.) Average speeds on such 55-mph roads thus are likely to be higher than speeds in states where there are many rural, two-lane, 55-mph zones.

The state takes readings at 28 points throughout Maryland using magnetic induction loops buried under the highway. When Shah noticed that too many drivers were going too fast, he quickly alerted state police. Thus began the crackdown.

As Cpl. Etheridge was sitting in the pickup the other day, he kept one eye on his rear-view mirror and the other on a digital readout from the radar.

And as the cars sped by, he radioed to the troopers ahead: "Black pickup truck, going 71. He has a white car going 68 just behind him." As the two vehicles rounded the corner and saw the troopers, he could see their brake lights come on. But by then it was too late, and they were hauled to the side of the road.

Carlton E. Brooks, a 25-year-old courier running a message, was hauled aside and given a ticket that would cost him $40 and 2 points on his driver's license. "I was going 61, and they said I was going 69," he complained. "I knew I was maybe a dot over 60. I'm ahead of my schedule. I'm not in a hurry at all."

In a little more than an hour, with Etheridge working the radar, troopers Richard Puffenberger, Karen Fortune and Chuck Ruby had written 23 tickets for speeds between 67 and 76. They did not stop anyone going slower than 67, because there were just too many people speeding faster than that to stop them all.