A new proposal to reconstruct a crumbling stretch of the Brooklyn Queens Expressway would convert the triple cantilever into a three-tiered park and expand into Brooklyn Bridge Park with six acres of new green space.

The plan, crafted by longtime Brooklyn Heights resident Mark Baker, would create an “aboveground tunnel” by relocating the BQE to a new, expanded road on Furman Street and then deck over the structure to connect the lowest level of the triple cantilever to the waterfront park. The new expressway would be encased in a “box-like” structure equipped with technology to filter fumes from some 153,000 vehicles driving on the road each day.

Baker, 64, says the concept, which he has dubbed the tri-line plan, would kill two birds with one stone by creating miles of parkland while working to improve the area’s air quality. He points to Manhattan’s High Line as an example of a dramatic reimagining of dated infrastructure becoming a boon for the neighborhood.

“I’m saying why don’t we take this historic structure that Robert Moses created, the triple cantilever, and historically reuse it as linear parks?” said Baker, who was once the chairman of the Brooklyn Bridge Park Conservancy’s board of directors and also helped create New York Water Taxi. “If I suggested that to you ten years ago you might have thought I was crazy, but with the success of the High Line, I think New Yorkers can see that it’s in everybody’s interest to take these unused transportation structures and turn them into parks.”

The idea came to Baker while he was jogging through Brooklyn Bridge Park last fall. He’s been working to fine tune the proposal with various experts in engineering, urban planning, and even botany over the last six months.

It’s the latest in a string of alternatives to the city’s pair of contested proposals to rebuild a 1.5-mile span of the highway between Atlantic Avenue and Sands Street. The city’s plans would temporarily tear down the Brooklyn Heights Promenade in years-long construction projects—one would replace the esplanade with a temporary, elevated expressway practically on Brooklyn Heights residents’ doorstep. Baker doesn’t have a timeline or price tag estimate for his plan but believes it will be “much shorter and much cheaper,” he said.

To build the new road under the so-called tri-line plan, a strip of parking between Brooklyn Bridge Park and Furman Street would likely need to be eliminated to place three lanes of traffic in either direction on the street. The structure boxing in the expressway would include a system to help filter exhaust from vehicles. One method Baker looked at, for instance, could involve a device known as an electrostatic precipitator, which uses an electric charge to eliminate particulate matter.

Most importantly, the plan wouldn’t shutter the Brooklyn Heights Promenade and would eliminate the “agony” of temporary highways during construction, says Baker. (The city says the promenade would eventually need repairs of its own even if it’s not touched during the reconstruction.) The lower tiers of the triple cantilever would be transformed into miles of green space and would actually connect with the Promenade and the sweeping new acreage of Brooklyn Bridge Park, according to Baker. And he believes builders could get creative with how they link the spaces.

“My personal favorite would be to put a slide at the promenade so you could slide down into Brooklyn Bridge Park,” said Baker, who has lived on State Street for 40 years with his wife and three sons. “But you can imagine the creative ideas park designers could come up with to program those 1,800-foot long sections.”

The Brooklyn Bridge Park Corporation, which operates the park, did not immediately return requests for comment. Baker is in the process of preparing his plan for submission to the city’s Department of Transportation, which says it is in the midst of a “thorough review process that will look at range of options,” according to Alana Morales, a DOT spokesperson.

Comptroller Scott Stringer has suggested a similar plan that isn’t quite as bold as Baker’s, but is equally ambitious in pushing for new greenery in place of gritty roadways. Stringer’s vision would convert the triple cantilever and the Cobble Hill trench—a depression of the BQE that runs from Congress Street to Hamilton Avenue—into a truck-only highway topped with a nearly two-mile-long linear park.

Baker says his plan is “totally compatible” with Stringer’s approach, but says he thinks the Comptroller’s concept should go further, and hopes input from local community groups and residents will help shape the plans moving forward.

“I say, ‘Why don’t we go the whole way?’” he said. “I think it really takes a community based solution to think out of that box to come up with something that’s better.”