A national team of planners recommended a design yesterday that would transform K Street NW into a tree-filled, urban "Main Street" designed to attract activity day and night and give Washington's downtown district an identity.

After a three-day cram session, the planners laid out a vision for "A New Way on K" between Washington Circle and Mount Vernon Square. The plan includes widening sidewalks to allow for outdoor cafes, splitting the road into separate avenues for car and transit traffic and lining medians with hundreds of trees and extensive ground-level landscaping.

The planners envisioned a transit- and pedestrian-friendly boulevard with a "green" theme that would link it to the three parks that line its sides so that they would be integrated into the road, rather than serving as a refuge from it.

The design would rid the street of its four service and parking lanes, which the team described as a "disaster" because they fail to serve retailers and contribute to traffic tie-ups.

The plan, similar to one put forward by District officials two years ago, would remake one of the city's critical traffic arteries. K Street serves as an entry point for drivers coming into downtown Washington, especially those funneled onto it from the Key Bridge, and a major east-west thoroughfare for them once they hit the city's core. As such, it is also used by several bus routes.

The road itself is split into three sections: a service lane and a parking lane on either side, separated from four lanes of traffic by small median strips. Beyond its functional detail, K Street is famous across the country for being home to lobbyists, lawyers, interest groups and all manner of Washington power.

But the planning team said that its cachet lies more in "name, perhaps, than reality" and that a redesign is needed to turn it into the centerpiece boulevard it ought to be. "What we see today is a space squandered," said Theodore Wolff, a principal with Wolff Clements and Associates in Chicago. "We see something with a lot of unrealized potential."

The group, which included planners from Boston, Chicago and Seattle brought together for $20,000 by the National Capital Planning Commission and the Downtown Business Improvement District, delivered a stinging critique of the K Street of today. The planners said that in trying to do too much, K Street accomplishes very little. Buses crowd the right lanes, turners crowd the left lanes, all kinds of vehicles crowd the service lanes, and parking is consumed by meter-feeding delivery and construction vehicles.

They also poked fun at "vendor sprawl," saying that the ever-multiplying carts, their trash and their drink coolers consume too much sidewalk space, and they mocked the stumpy, concrete ballasts that line the street's medians. The ballasts exist to prevent drivers trapped in the service lanes from escaping by wheeling over the median.

The planners also questioned the wisdom of launching a new, low-cost circulator bus route on K Street next year. Linda Fuller, an executive with the Chicago Transit Authority, said it would be difficult to persuade customers that a 50-cent, tourist-style bus route running between Union Station and Georgetown would be different from regular service if it went on the same, gridlocked road. She also said it would hinder enthusiasm for similar efforts in the future and suggested running the buses on the one-way parallels of L and I streets in the interim.

The District's director of transportation, Dan Tangherlini, said he would "go back and definitely look at that."

The plan would give K Street a look similar to what it had at the start of the 20th century, when large, overhanging trees provided a canopy for cars. By the mid-20th century, it was rebuilt to its current design.

"It was a very [1950s] modern notion of a world dominated by cars," Tangherlini said. The central lanes were to become part of a freeway system, and the service lanes were designed to handle local traffic, he said.

The conclusions of the planning team generally reflected the District plan announced two years ago, which also would eliminate the service lanes in favor of running transit lines down the center of the roadway. But the new recommendations differed by trimming the width of road lanes and eliminating a parking lane in favor of wider sidewalks and medians.

Rich Bradley, executive director of the business improvement district, said that while the planners did a good job of solving concerns for the general public, "they didn't think as affirmatively about what the solution would do for commercial property owners."

For instance, the planners' proposal to eliminate all parking and deliveries from K Street would require businesses to make alternative arrangements.

The planners suggested those be shifted to side streets, but some of those, such as Connecticut Avenue, are also major traffic arteries.

"I think their plan would make K Street an amazingly beautiful street," said Tangherlini, who estimated its cost at $30 million, similar to the price put on the city's idea. "The question is how we can work through that with the people who use it now and rely on it now."

He said the District hopes to begin construction of a redesigned K Street by the middle of 2006.

K Street NW, shown here looking west from Vermont Avenue, is "a space squandered," said Chicago landscape architect Theodore Wolff.