Prince George's County officials said this week that they did not formally oppose the federal government's proposal to convert highway signs to metric measurements, as reported June 30 in the Maryland Weekly. John C. Rice, chief of the Prince George's traffic operations division, said he was mistaken when he told a reporter that a letter he drafted for the signature of his boss, Donald R. Dunker, director of public works and transportation, has been signed and sent. Dunker said he neither opposed metric conversion in principle nor disagreed with the staff recommendation, which opposed the highway sign plan as too costly and too soon. "The county had not really taken a position," Dunker said. "I thought the staff position got into some areas such as financing that should be made by the county executive . . . We are not opposed to the metric system, but we do have problems with the timing and the financing (of the highway agency proposal.)"

Confronted with objections from local and state governments including Prince George's County, the Federal Highway Administration has abandoned a plan to require that all highway signs use metric measurements by late 1982.

The action will probably lead other federal agencies to "stop and think" before they propose similar metric conversion plans, according to Richard Reilly, public information officer for the highway agency. He said the Metric Conversion Act of 1975 established metric conversion only as voluntary national policy, not binding law.

The federal plan called for converting all speed limit signs to metric measure by the end of 1979, and all other regulatory and advisory signs by late 1982. It was killed because of objections based both on cost and safety.

Earl Johnson, a Federal Trade Commission attorney who is a member of an interagency committee studying metric conversion, suggested that the highway agency "took people by surprise" before they were accustomed to using kilometer speedometers and measurements.

"You've got a study in human nature," he said. "We've got a long period (of metric conversion) ahead of us, but it's going to come by bits and spells. Johnson noted that most metric conversions will require cooperation between government and private industry.

Prince George's County officials found the timetable and the costs of the plan particularly troublesome; the county protested the plan and listed its objections in a letter by D.R. Dunker, director of the county depart- ment of public works and transportation.

Federal officials said last week that approximately 5,000 "highly negative" comments such as those by Dunker led to Federal Highway Administrator William M. Cox's decision to abandon the plan.

The conversion would have forced some changes in speed limits, highway sign formats and automobile equipment; for example, the 55 miles per hour speed limit would have become 90 kilometers per hour, which works out to about 56 1/4 miles per hour.

Also, metric speed limits on signs would have been followed by the designation "km," standing for kilometers-per-hour. Owners of autos more than two years, which do not have kilometers-per-hour markings on their speedometers, would have been required to obtain a paste-over kilometer scale for the speedometer.

John C. Rice, chief of the Prince George's County division of traffic operations, estimated that it would cost the county $175,000 and take eight man-years to change the county's 4,000-plus speed limit signs. He called the cost "quite staggering" and said the federal plan did not give the county enough time to prepare for it.

Rice also questioned the federal agency's proposal to make the change to the metric system immediately. He said there should first be a public education program, and he also suggested that metric signs should follow a special format - for example, horizontal rather than vertical speed limit signs.

Rice said metric signs would present a "behavior problem" for motorists used to the current signs. For example, a warning sign advising motorists to slow to 40 miles per hour on a curve would be changed to advise a speed of 65 or 70 kilometers per hour. That could confuse a motorist driving 50 miles per hour, he said.

In Montgomery County, Bill Klein; assistant chief of the traffic engineering division, found fewer problems with the federal proposal than Rice though he did not officially study it or that any change should be made gradually, with a transition period during which both old and new signs are displayed.

Slade Caltrider, district engineer for the Maryland highway administration, said the state did not formally comment on the federal plan.But he said his department "could not change our signs in a very short time" because of the number of signs and the inaccessibility of some of the big highway signs.

In the District, officials said they could handle a change if made gradually, but in Virginia state officials strongly protested the federal proposal, saying it would cost them $17 million to change all state highway signs.

Reilly said opposition to the agency's proposal also came from several congressmen who thought the proposal went beyond the voluntary conversion policy of the Metric Conversion Act of 1975.