After decades of discussion, debate and expectation, the Arlington County Board has approved a plan to redevelop Columbia Pike.

Last week, the board unanimously approved a slate of guidelines to direct developers who hope to build along the 3 1/2-mile corridor that cuts through South Arlington and is now a mishmash of faded art deco facades, World War II-era apartment buildings and vacant lots.

Supporters say the guidelines, known as a "form-based code," will help developers and builders create a unified design for the four-lane road, which has been passed up for major development for nearly 30 years.

While the guidelines focus mainly on development details -- allowable facades, location of trees and size of window spaces -- the plan's vision is nothing if not ambitious. The barren intersection of stores and apartments at George Mason Drive and Columbia Pike, for instance, becomes a lush and bustling street corner. Dowdy, pockmarked small businesses near Walter Reed Drive morph into vibrant mixed-use shopping and living quarters. The intersection of Columbia Pike and Glebe Road transforms into a commercial hub.

Although several projects are being considered and one mixed-use project was approved last week, county leaders said they do not know how long it will take for this vision of the pike to materialize. Much will depend on market forces and the county's own moxie in encouraging developers to believe in the process, community activists and officials said. Optimists said that within five years, 1 million square feet of retail and commercial development could be built along Columbia Pike.

At last week's board meeting, Timothy Lynch, director of the Columbia Pike Revitalization Organization, which helped to organize the guidelines, gave a series of impassioned thank-yous to those who had a hand in the decades-long process. Former county staff member Bob Rulli, who helped to usher in the pike's latest development plan and now works in upstate New York, returned to Arlington just to see part of what he started approved. There were even kudos from the most grizzled county residents and activists.

"This process has been astounding to me," said Randy Swart, a community organizer who has lived in the county for nearly 50 years. "Just a month ago, a lot of people were rolling their eyes and saying, 'This is not ready for prime time.' "

Concern remains about the impact of the plan. Will the infusion of major development displace the largely immigrant population that has come to the pike for its relatively cheaper apartments, for example?

In a letter to the County Board, neighborhood activist Todd Endo expressed concern about the board's objectives for affordable housing and ethnic diversity in the corridor now home to people from 128 nations.

The board needs to consider more concrete goals for "build[ing] upon the asset of ethnic diversity in its commercial redevelopment . . . retain[ing] and expand[ing] community-based small businesses, ensuring affordability and continued diversity," Endo wrote. "While we have proceeded well through the process, we have not brought the vision statement down to enough specifics."

Others expressed skepticism about whether parking issues were addressed adequately. Many are concerned that, in trying to encourage pedestrian activity, the county will not provide enough garage space. In addition, bicycle activists expressed concern about whether streets would be wide enough to facilitate bike traffic along the pike, which they describe as a difficult corridor to navigate.

County Manager Ron Carlee told the board that parking plans were still being finalized but that the county staff would submit a formal proposal requiring permits for nighttime parking in residential areas within the month, with a more detailed parking agenda to come by May.

In addition, the development plan calls for a program whereby residents could use business parking spaces at certain times of day.