ANNAPOLIS, MAY 30 -- When Del. Dennis C. Donaldson began working today at the Maryland Department of Transportation, he was trodding a well-traveled road that leads from the Maryland General Assembly to other branches of state government.

Donaldson, a Prince George's County Democrat who served three terms in the House, cemented his decision not to seek reelection to his $25,000-a-year House seat when he was offered roughly $64,000 to take the newly created post of special adviser to Secretary of Transportation Richard H. Trainor.

"It seemed like the right thing to do at the time," said Donaldson, who will advise the secretary on legislative matters and maintain contact with political leaders. "It was time to do something else."

The right time comes with some regularity to Maryland state lawmakers, many of whom make the transition to administrative posts or judgeships. No definitive records are kept, but lawmakers quickly point to dozens of former colleagues who moved into other state posts.

"It most frequently occurs when a legislator, for reasons of redistricting or dramatic changes in their district, has the liklihood of not being able to come back," said House Minority Leader Ellen R. Sauerbrey (R-Baltimore County). "When the legislator is well liked . . .they try to find a soft landing spot."

William R. McCaffrey, a legislator from Prince George's, for example, landed a job last fall as executive assistant to the state railroad administrator just as fellow legislators from his district were preparing to replace him with a minority candidate on their ticket.

Jospeh E. Owens, a Montgomery County Democrat and the longtime chairman of the House Judiciary Committee, became deputy secretary of the Department of Licensing and Regulation after being upset in his 1986 bid for reelection.

And the ranks of recent judicial appointments are packed with former legislators, including Gerard E. Devlin in Prince George's, Raymond E. Beck in Carroll County and John C. Coolahan in Baltimore County.

"This is what's called 'going to your just reward,' " said one legislator.

The appointments usually cause little stir, but the salary to be paid to Donaldson, a retired D.C. police detective sergeant, did raise some eyebrows.

"The issue is are we just creating a position and adding it to the tax and spending problem to take care of someone," Sauerbrey said.

Senate President Thomas V. Mike Miller Jr. (D-Prince George's) praised Donaldson and said the new post he will hold has been sorely needed in the Transportation Department.

"I'd only be troubled if the person were not qualified," Miller said. "If it were simply a sinecure, then not only would I disapprove, but I'd voice my opposition."

The many appointments of lawmakers to judgeships, Miller said, are a natural transition for lawyers, who account for 21 percent of the General Assembly.

Sen. Victor Cushwa (D-Washington County), who once publicly criticized the appointment process as being open to cronyism and political favoritism, is the leading candidate for appointment next month to a $73,755-a-year seat on the Public Service Commission.