Advocates of building a Purple Line between Montgomery and Prince George’s counties have long argued that a light-rail line would move people between the Maryland suburbs more quickly and reliably than buses stuck in traffic.

Now that the project has received federal environmental approval and, more significantly, a formal recommendation for $900 million in federal construction aid the focus is turning to how a Purple Line would remake communities along the 16-mile alignment.

A key benefit of building a transit line, community planners say, is the chance to attract economic development around stations. But how do you keep gentrification from pricing out the people now living in more affordable apartments in areas such as Long Branch and Langley Park? How do you help people of all income levels benefit from the job opportunities and economic development that a rail line would bring?

And how do you help the businesses that would have to live through several years of construction survive when the street in front of their storefronts are torn up?

About 260 local officials, planners, nonprofit leaders, economic development officials, private business people and transit activists gathered at the University of Maryland on Friday to discuss some answers. The title of the all-day workshop: “Beyond the Tracks: Community Development in the Purple Line Corridor.”

“The Purple Line represents a once in a lifetime opportunity to transform south suburban Maryland into a more prosperous, vibrant and equitable area of the DC Metro region,” said Gerrit Knaap, director of the university’s National Center for Smart Growth.

The line, which would cost an estimated $2.37 billion to build and another $69 million annually to operate, would run between Bethesda and New Carrollton. The 21 stations would include North Chevy Chase, Silver Spring, Long Branch, Langley Park, College Park and Riverdale Park. It would connect Maryland’s spokes of the Metrorail system with Amtrak and MARC commuter rail stations.

Opponents say the rail line would destroy a wooded jogging and bike trail between Bethesda and Silver Spring, bring too much noise and train vibration to nearby residents and be inordinately expensive compared to a cheaper bus option. Some local environmental activists also have said they’re contemplating a lawsuit over a Purple Line’s potential impacts on the endangered Hay’s Spring amphipod.

The group gathered Friday — almost all, apparently, avid Purple Line supporters — heard from officials from Denver and the Minneapolis-St. Paul area, where rail lines have recently opened and are still under construction. Their advice: Think of the 16-mile alignment as one economic corridor for transit-oriented development, start thinking now about an assistance program for affected businesses, and make sure leaders from different fields (transportation planning, community planning, health, private business, nonprofit groups) are all working together from the get-go.

“There is going to be disruption,” said Mary Kay Bailey, who oversees community issues along transit lines in the Minneapolis-St. Paul area. “It is going to cause fear, and it’s going to be tension-laden.”

Knaap showed the group data from his University of Maryland graduate students’ research showing the diversity along the Purple Line corridor, from wealthier communities on the west end, such as Bethesda, to lower-income areas in Long Branch and Langley Park. What the communities have in common, he said, was the number of jobs clustered around them.

The Purple Line would link those job centers, making the corridor one of the biggest economic engines in the state, he said.

“Think about the potential of Bethesda and Silver Spring when the two dominant economic centers in the state become linked by the Purple Line,” Knaap said.

Local officials also apparently have another question in mind: How do you make these new transit-oriented communities vibrant, walkable places where people will want to live, work and hang out? (Or, as one speaker put it, “So we don’t end up with a bunch of condos over jewelry stores.”)

Organizers said an afternoon session on “place making” was expected to draw the biggest crowd.

As Knaap put it: “We have a real opportunity to build a new urban fabric.”