Metro officials, seeking to end a protracted controversy, have recommended spending millions of dollars a year to equip half of the transit system's buses with special lifts to accommodate passengers in wheelchairs and other disabled riders.

The compromise proposal would result in a sizable increase in the number of Metrobuses with lifts, but it would fall short of demands by some critics who have contended that all buses should have lifts. Metro General Manager Carmen E. Turner has termed the plan a "significant improvement."

The proposal, expected to be considered this week by a special committee of Metro's policy-setting board, stemmed partly from a $90,000 consultant's study. The 211-page report found that most moves to improve service for handicapped bus riders would likely prove costly and raise thorny issues.

The study, by Ecosometrics Inc., a Bethesda firm, estimated that it would cost $5 million a year to provide lifts on 50 percent of Metro's buses by the mid-1990s. According to the report, this cost is equivalent to about $27 for each bus trip by a handicapped passenger who uses a lift.

To install lifts on all Metrobuses would cost nearly $10 million a year, or about $37 for each ride, the report said. The study provided no overall recommendations, but it described the 50 percent level as "the most cost-effective" for lifts.

The consultants also suggested considering a "paratransit" system to provide door-to-door service for disabled passengers in vans, taxis or other vehicles.

Metro officials rejected this option, saying that similar services are provided by more than 100 local social service and other agencies.

Frances H. Lowder, who heads an advisory committee of elderly and disabled Metro riders, said the panel is "leaning toward" supporting the 50 percent target but probably will urge steps to reach that goal sooner.

One possible option, she said, is to require all buses purchased by Metro in the next few years to have lifts.

"It's probably going to be a long time coming, to get to 50 percent," Lowder said. But she added, "It would be a massive improvement in flexibility over what is available now."

Mary Margaret Whipple, who heads the Metro committee weighing the issue and is scheduled to become Arlington County Board chairman tomorrow, termed the Metro plan a "middle-of-the-road proposal." It would "not serve all the need," she said, but it would "take care of a substantial proportion."

The debate over installing lifts has been a controversial one. Last year, a Denver-based group called ADAPT, an acronym for American Disabled for Accessible Public Transit, staged demonstrations here marked by disruptions in rush-hour bus service to demand improvements for handicapped riders, including lifts on all buses.

Metro and other transit systems face a federal mandate to make special efforts to accommodate disabled passengers.

Although the U.S. Department of Transportation has not issued final rules, Metro officials said, the 50 percent plan appears likely to comply with current federal proposals.

In contrast to the controversy over bus lifts, most disputes over access to the subway system for disabled riders were largely settled in the 1970s as a result of court challenges that led to the installation of elevators for handicapped passengers and other measures.

The Metro system now has 225 buses with lifts, 14 percent of its 1,572 vehicles, according to the new study.

The lifts have long been plagued by malfunctions, and many of the lift-equipped buses have been out of service for repairs because of cracks and other defects largely unrelated to the lifts.

Officials said Metro plans to buy about 100 more buses with lifts soon. The agency now dispatches 52 lift-equipped buses on daily routes and uses an average of 56 in its "On-Call" service, a program that allows disabled patrons to phone one day in advance to request lift-equipped buses on other routes.

The consultant's report said that Metro now spends $1.4 million a year for lifts, estimated to cost $15,000 each, and for other bus services for the handicapped. Thirty-three disabled passengers take trips every day on Metro's lift-equipped buses, the report said. Others use the lifts for occasional rides.

If all Metrobuses had lifts, the study said, the lifts would be used about 900 times a day by handicapped riders.

Under the 50 percent plan, it indicated, the lifts would be used nearly 640 times a day, about 30 percent less often.

The study said 47,197 "ambulatory disabled" residents, age 16 and older, live in the area served by the Metro system, or 2.2 percent of the population. Of that total, 2,288 residents use wheelchairs, 13,319 use canes, walkers and other devices and 31,590 do not use such aids.

Only a portion of these disabled residents would benefit from lifts on buses, the study said. Many with relatively moderate disabilities do not need lifts.

Others are unlikely to take a bus because they have difficulty getting to a bus stop, lack sufficient stamina for a trip or face other problems.

In their proposal, Metro officials recommended purchasing lifts at a rate of 50 percent of the buses the agency buys each year until half the total fleet is equipped with lifts. The long-range plan is similar to a move adopted by the Metro board in February as a temporary strategy for buying buses.

Metro officials proposed retaining the current system of splitting the lift-equipped buses between regular routes and the "On-Call" program, and they suggested steps to improve maintenance of lifts and training for drivers in operating the lifts.