Broad Branch Road has a flood-damaged stretch of road that serves as both a commuter connection and a route into Rock Creek Park. (Bonnie Jo Mount/The Washington Post)

Running for a mile and a half alongside Rock Creek Park, Broad Branch Road is, in many ways, a classic country road in the middle of the city. Narrow and winding, it is tucked among the wooded hills of the park and mid-century homes, a few scattered embassies and the former estate of Marjorie Merriweather Post.

Picturesque as it is, Broad Branch has become a commuter route, carrying thousands of people who use it to bypass Connecticut Avenue and 16th Street in upper Northwest Washington. The signs of age and heavy use are evident. Chunks of the retaining wall that runs along the serpentine creek bed at the park’s edge are falling off. The road — marked with potholes and worn edges — frequently floods. And pedes­trians and bicyclists complain that there’s no room for them on the stretch of shoulderless road, as it runs from Linnean Avenue to Beach Drive.

Now the District Department of Transportation is considering an extensive rehabilitation that could include adding a sidewalk and a bike lane. The department is expected to chose between one of four alternatives early next year, the most expensive of which would cost $37.1 million and take three years to complete.

All three of the “build alternatives” would include an expanded retaining wall, a replacement for the damaged Soapstone Branch culvert, which collapsed in April 2011, and at least the option of adding a stop sign for traffic at the Brandywine Street intersection.

The most ambitious of the plans, Alternative 4, would also add a bike lane and sidewalk for the entire length of the road.

After the no-action alternative, the least ambitious plan, Alternative 2, would make the structural improvements while providing an option to add a stretch of sidewalk from the culvert to the parking lot just north of Beach Drive. That plan would cost $29 million.

When the District Department of Transportation decided to study possible improvements to the road, it had three main goals in mind: to improve the deteriorated pavement and poor drainage, to create a safer experience for all users; and to provide better connections to and from the park for pedestrians and bicyclists.

But opponents of the proposed plans are worried about the loss of trees, which could range from 240 to 460, depending on which construction plan is approved.

Casey Trees, an environmental advocacy group in the city, argued that Alternative 2, which would add a curb and gutter to the narrow street and extend the retaining wall, would be the best and least disruptive option because it improves the road without clearing too many trees.

“Broad Branch Road,” wrote Maisie Hughes, the group’s director of planning and design as part of the project’s public comments, “is a low speed, local road with scenic views of the park. Alternative Two best maintains the character of this road.”

At the most recent public hearing in November, about 20 people spoke from a crowd of 80. In the following 30 days, DDOT received 250 more comments, most from neighbors of the road rather than people who use the road simply as a throughway.

Program manager Paul Hoffman said support was divided but that most Advisory Neighborhood Commission and other community groups have come out in favor of building a sidewalk and a bike lane.

The city’s Bicycle Advisory Council came out in support of the bike lane plan, but according to Ellen Jones, the chairman and Ward 3 representative on the council, the issue of tree loss became a sticking point at the public hearing. “There were very strong differences of opinion,” she said.

“I’m not for tree removal,” said Jones, who lives in Chevy Chase, “but if the outcome that we’re looking for is to make this national park more accessible for people by bike and by foot, that’s a big thing in terms of both quality of life for people who live in the immediate area, as well as accessibility to natural space.”

Jones, who lives a 10-minute bike ride away from Rock Creek Park, rides the route roughly once a month. “There’s not good sight lines, there are pinch points,” she said. “The uphill experience is not a happy one coming out of the park, and yet you don’t really have a choice.”

Even midday on a recent Thursday, the road was busy. Every 30 seconds or so, a car came speeding around one of the curves, which are marked by a few feeble, yellow signs warning drivers to slow to at least 15 mph. About 4,200 cars use the road daily, according to DDOT’s 2011 weekday counts.

The most pressing concern for Hoffman, the program manager, is the Soapstone Branch culvert. A 2011 fix added a liner to support the bridge, he said, but that liner narrowed the space the creek can travel through, making flooding even more likely. DDOT was actually eyeing the culvert for repairs or replacement when it collapsed.

But 10 inches of the stone structure reside on National Park property. “If it was totally on D.C. public space, we could’ve done what we wanted.”

After DDOT selects its preferred plan in early 2014, it will seek U.S. government approval.

Jones said that because Broad Branch is as busy as it is, it’s worth taking the time to do the repairs so the road can better serve all users. “If you added up all the times that the road gets flooded and then this most recent occurrence, when it was really serious,” she said, “it’s the logical thing to do — to rebuild that road. So it’s entirely appropriate that the time be taken to do it right.”