The Arlington County Board, responding to complaints from the disabled, decided yesterday to include a bus with a wheelchair lift as part of a shuttle system in Crystal City.

"I'm gratified," civil rights attorney Jill Robinson, who uses a wheelchair, said after the board's action. Robinson, who lives and works in Crystal City, and other speakers at yesterday's meeting said the current shuttle system is impractical and discriminatory.

"The system does not even permit me to go to the back of the bus. I cannot get on the bus," she said.

The current shuttle system comprises two trolley-like buses that loop around Crystal City.

Because the buses do not have wheelchair lifts, disabled people must use a backup service that requires 24-hour advance notice.

County officials had suggested shortening the reservation time to 90 minutes, but the board instead unanimously voted to provide a bus outfitted for the disabled, which is expected to cost $30,000.

"This is an opportunity to do something very positive," board Chairman John G. Milliken said.

The shuttle was started in November as an eight-month experiment to help reduce parking problems and facilitate getting around Crystal City. The board will decide later this year whether to continue the service, which has proved popular with Crystal City residents, workers and shoppers.

In other action yesterday, the board unanimously approved a 176-unit residence for the frail elderly to be built on the former site of the Calvary Church of the Nazarene on Wilson Boulevard and N. Manchester Street. The $15 million project is being undertaken by Sunrise Retirement Homes, which is also building a 50-bed facility for the elderly on North Glebe Road.

In 1986 the board rejected a proposal by Arlington Hospital to build a larger retirement complex and nursing home on the Wilson Boulevard site. Neighbors had objected to the size of the hospital's proposed project.