The Falls Church City Council Monday night adopted 5 to 1 a resolution that calls for the reconstruction, including the addition of a fifth lane, of a half-mile stretch of western Broad Street (Rte. 7), the major artery through the city's business district.

Adoption of the proposed road plan, which will be forwarded to the state highway department for final approval, ends months of meetings, public hearings and work sessions on one of the most important issues to come before the city this year. City officials and residents have agreed for years that Broad Street needs improving, particularly its paving, drainage and unsightly utility wires, but they have disagreed on whether the road should be widened to include a fifth turning lane.

City planners and some citizens have said that traffic congestion, especially at rush hour, makes it crucial to add a left-turn lane to keep traffic moving and motorists from taking shortcuts through residential areas. Some city preservationists, on the other hand, have argued that a wider road at the western edge of the city would attract more and faster traffic and destroy the city's small-town atmosphere.

Mayor Carol DeLong, who heads the council, admitted that the decision to include the fifth lane had not been an easy one.

"It's been a tough summer," she said. "There are very hard and concrete differences of opinion."

The road plan focuses on the half-mile stretch of Broad Street from Haycock Road to West Street, the first phase of a three-part plan to improve Rte. 7 from I-66 to Fairfax Street. It calls for the addition of the fifth lane, which will be a two-way left-turn lane with extended raised medians at two places -- where Broad Street intersects with Haycock Road and with West Street. The plan also calls for significant streetscape improvements and a better synchronized traffic light system.

The work, which will cost the city about $2.2 million, is scheduled to begin in 1987.

"I could only vote for a proposal that would include a fifth lane for turning vehicles," said council member Elizabeth Blystone. "There's a real need for that lane, certainly during rush-hour."

Council member Gary Knight, who voted in favor of the resolution, said that the increase in traffic expected when the West Falls Church Metro station opens next summer was one of several reasons he felt a fifth lane was necessary.

"As bad as the situation is now, it's going to get worse," he said.

Council member Edward Strait cast the dissenting vote.

"I remain opposed to the fifth lane," he said. "I'd rather have four congested lanes than five," he said.

Virtually all the council members, including Strait, said they had been impressed with the summer-long process of meetings and opinion gathering.

"I have never felt so comfortable about a major decision," said council member W. John Cameron. "The process we've been involved in has been excellent."

But Louis Olom, a member of the Village Preservation & Improvement Society, who has strongly opposed widening, did not agree. At the meeting, he appealed to the council to hold a referendum on the widening issue.

"Your decision will be a legacy that you will bequeath onto future generations that will rank in infamy with that of the first council that also knew best when it strip-zoned Broad Street," he said. "And now you want to convert it into a boulevard of broken promises, a boulevard of broken dreams."