Gasoline lines were shorter in many parts of the Washington area yesterday as the first day of a government-imposed odd-even gasoline sales plan here apparently brough relief to motorists.

Lines of waiting cars shrank, drivers smiled and police reported widespread compliance with the new odd-even rules - the first imposed here since the Arab oil embargo in early 1974.

Under the plan jointly implemented by the governors of Maryland and Virginia and the mayor of the District of Columbia, only drivers with odd-numbered license plates could buy gas yesterday, an odd-numbered day of the month. Today, drivers with even-numbered tags get their chance at the pumps.

Many service station dealers pronounced yesterday a success, said gas lines were noticeably shorter and even stretched their hours of operation in some cases. A few other dealers said they saw little change from previous days.

"People have a different attitude now," said James Jones, and attendant at the Arco station at 18th Street and Rhode Island Avenue NE. "They're talking to you. They're friendly, and it seems like a new year."

While motorists seemed cheered yesterday, the outlook for this weekend continues to be grim. The American Automobile Association said service stations in the immediate Washington area should be open at about the same rate as last weekend - 63 percent on Saturday with only 16 percent staying open after 6 p.m. and only 6 percent open at all on Sunday.

Gasolina should be more available in outlying areas beyond Washington and Baltimore, the AAA said.

Both Saturday and Sunday are "open" days under the odd-even plan, permitting all drivers to buy gas regardless of license number.

While there was general relief at the pumps yesterday, there was also some confusion. Police and other authorities were swamped with calls. Drivers demanded clarification about the odd-even plan about exemptions, about license tag numbers, about minimum purchase requirements. Maryland, Virginia and District officials rushed copies of guidelines and executive orders to the public, and a whole new paperwork bureaucracy was born.

Also, state officials and some members of Congress continued to question the legitimacy of the current fuel shortages and to press federal energy policy makers for changes in gasoline allocation rules to help the Washington area.

Virginia Gov. John Dalton, Maryland Gov. Harry Hughes and D C. Mayor Marion Barry are scheduled to meet with Energy Secretary James Schlesinger here today at 2 p.m. Sen. Charles McC. Mathias Jr. (R-Md) also announced a meeting between Schlesinger and the Maryland-D.C.-Northern Virginia congressional delegation next Wednesday at 1 p.m. on Capitol Hill.

An urgent letter to President Carter signed jointly by Dalton, Barry and Hughes apparently triggered the meeting with Schlesinger set for today.

In the letter, the three chief executives objected to 1977-78 D.C. area fuel consumption statistics used by the Department of Energy to help determine gasoline allocations for this year. They contended the statistics were unadjusted for the area's economic growth.

Also, they complained that DOE's base period for determining allocations is a "winter base" that tends to favor greater allocations for areas with warmer climates and heavy winter tourist business.

The Washington area joins a growing number of regions in the country that have adopted odd-even gas sales plans in recent days. Connecticut and the New York City metropolitan area went to odd-even Wednesday. The city of Miami and New Jersey joined yesterday.

Fifteen counties in California have been under an odd-even plan for several weeks.

In the Washington area yesterday, most service station dealers interviewed reported general compliance with the new plan. Some said they did not try to enforce the plan when cars with even-numbered tages showed up.

"I'm not going to enforce it," said Jum Ott, manager of the B.P. station at Connecticut Avenue and Albemarle Street NW. "Somebody could get killed . . . There's got to be something better."

Ott was one of the few managers interviewed who said the odd-even plan had no effect on the long lines at his station.

"I opended at 5:30 and closed at 8 this morning," he said. "It was the usual thing. Everyone, I pump 3,600 gallons and then I close about two and a half hours later."

"The line here is definitely shorter this morning," said Irvin Parsley, manager of Shepherd Park Exxon across Rock Creek Park at Georgia Avenue and Geranium Street NW.

"It (odd-even) worked in 1974," he said, "so it ought to work now."

Police reported few problems throughout the day. Under the odd-even executive orders issued by Goves. Dalton and Hughes, police are specifically empowered to enforce the plan, and violators can be fined up to $100.

In the District, Mayor Barry's order does not contain specific sanctions. D.C. police said that if a service station manager asked a motorist with a wrong-numbered tag to leave the station and the motorist refused, he could be arrested for unlawful entry, a misdemeanor.

"But we're looking for voluntary compliance," said Lt. Larry Soulsby, D.C. police spokesman. "That's the big thing . . . We'll do everything to keep from making an arrest."

Few motorists with even-numbered tags were seen in line yesterday. Pamela Lewis, a teacher from Newport News with even-numbered tags, said "Yeah, I know I'm supposed to be odd-numbered, but I've got to get back (to Newport News), and I've got less than a quarter of a tank left."

At the B.P. station at Wisconsin Avenue and Jenifer Street NW, a woman with even-numbered tags on her blue Futura sat behind the wheel, waiting patiently as the line moved slowly toward the pumps.

An attendant told her she had wrong numbered tags and would not be served. The woman look blankly at the attendant, not saying a word. As her car puller closer to the pumps, station manager LaCount Togans hailed a nearby D.C. policeman.

The policeman, A. A. Rivera, came to the car and began explaining the new odd-even plan. The woman, he discovered, was Spanish and spoke little or no English. She was not even aware of the odd-even plan.

Rivera, who happens to be Spanish speaking himself, quickly explained about "los numeros" to the woman. The woman broke into tears, a look a total confusion on her face. Moments later, she drove away.

"I don't understand that," said Rivera. "She had half a tank of gas."