At its traditional goal-setting New Year's Day meeting yesterday, the Arlington County Board elected John G. Milliken as its chairman.

Milliken, a Washington lawyer, leaves his position as the chairman of the Metro transit board to chair the five-member Democratic-controlled board.

"Like consumer prices and the Dow Jones," Milliken said, in 1985 the county should chart its successes according to "Arlington's livability index."

Topping Milliken's list of what would make Arlington more livable this year are improved transportation, more affordable housing and more retail services.

"It is time for the focus to shift . . . to where people live, where they shop and how they might travel from one to the other," he told the crowd of about 50 who filled the Court House meeting room at 11 a.m. yesterday.

Mary Margaret Whipple, after being elected vice chairman, said the board was also firmly committed to keeping Arlington's taxes the "lowest in the Washington area."

"The government across the river is placing a tougher burden on the localities," said Whipple, who has previously cited a recent board memo from County Manager Larry Brown, estimating that if federal cutbacks are enacted as suggested, Arlington could lose a minimum of $803,700 in fiscal 1986 and $4.8 million the following year.

Despite cutbacks, Whipple said the county will "continue to provide dependable services."

Outgoing chairman Ellen M. Bozman, who presided over the board for the last two years during a period of fast-paced development, agreed with Milliken that the "chapter on development" had not yet closed.

"The major development decisions are made," but there is still debate over "particular parcels" of land, said Milliken.

As construction continues to redraw the county's complexion, the board vowed to review a comprehensive traffic plan. The Master Thoroughfare Plan, as it was termed, would call for a comprehensive look at the county's network of streets, bikeways and walkways.

To alleviate other transportation problems, Milliken said, the county needed to toughen enforcement of the speeding laws and provide additional parking.

As in the past, the Arlington board said it would strive to encourage retail businessmen to relocate in the county.

Another ongoing effort -- accommodating the high demand for low- and middle-income housing -- will remain among the board's top priorities, Milliken said. "We need to make sure that Arlington remains a place where young families or their grandparents can afford to live."

"I live here and I work here, I guess that's why I come," said Karen Darner, a speech clinician for Arlington County schools who stood at the back of the board room. "I've done this for the last 10 years. . . . "