DDOT will spend much of its road stimulus money to completely reconstruct several roads, including Sherman Avenue, which we discussed recently. Another is 18th Street NW, from Massachusetts Avenue to Florida Avenue, in the Dupont Circle neighborhood. The 18th Street design contains some significant pedestrian improvements, particularly bulb-outs at many corners. DDOT engineers worked hard to design these improvements. Unfortunately, without clear principles for deciding when bulb-outs are appropriate or not, many of the key decisions came down to the last moment with little information.

Many parts of 18th are in bad shape, and WASA needs to completely replace a water main underneath the street. DDOT will rebuild all of the curbs, redo all sidewalks, tree boxes and streetlights, add bicycle parking and sharrows, and place multi-space parking meters along the metered sections. They will also create bulb-outs at many of the corners, which narrow the distance for pedestrians to cross by extending the curb in front of the parked cars.


Proposed design of 18th and T including bulb-outs and bicycle sharrows. (North is to the left.)


The project team worked very hard to keep almost all of the grassy triangles at 18th and New Hampshire. Right now, neighbors plant flowers in those small areas, but the curb ramps aren’t ADA compliant. Initially, DDOT engineers proposed considerably shrinking the size of those triangles, but found ways to adjust the ramps and comply with requirements while only removing small pieces of the green space.


Proposed design of 18th and Corcoran.  (North is to the left.)


Between one presentation and the next, the team suddenly changed the curb at the southeast corner of 18th and S Streets to have a much larger turning radius. Instead of a sharper corner with two ramps, that corner (at the upper right in the below drawing) has one larger diagonal ramp. What happened?


Proposed design of 18th and S. (North is to the left.)


I asked DDOT engineers about this at the meeting. They explained that unlike other corners like 18th and T, traffic heading northbound (moving left in the picture) hugs the curb since there is no parking lane, and therefore vehicles need a larger radius to avoid swinging into the opposite lane on S as they make the turn. Perhaps, but why so large, I asked? The corner of 18th and Riggs, where cars would turn onto a much narrower street, has the sharper corner.

DDOT engineers made time to meet with me one on one. They explained that the AASHTO guidelines call for a larger radius when two more major roads meet, unlike at Riggs which is a less heavily used road.  However, they added, AASHTO guidelines also allow for some flexibility, and they could sharpen the corner somewhat. Since large numbers of pedestrians walk through this corner, which is the southern end of the 18th Street commercial strip, designing it to let vehicles swing around the corner turn without slowing is the wrong design principle.

After presenting my concerns, the DDOT representatives told me that they would modify the corner to use a smaller turning radius. I’m very glad they agreed to this change, as it’s the right choice. However, is it really right to make this decision after talking to one resident? What if another resident had met with them and asked for a larger radius that encouraged faster vehicle traffic at another corner?

We need objective standards to make these decisions. The newly-finalized pedestrian master plan does address these issues, though in a general way. The section on turning radii contrasts the standard AASHTO manual’s recommendations, which suggest radii wide enough for all vehicles to “turn easily,” and the newer IT Context-Sensitive Solutions manual, which recommends radii wide enough for common vehicles but not necessarily all, and making walkable urban intersections as compact as possible.

The Master Plan recommends updating DDOT’s policies to match these best practices. It also addresses bulb-outs, also known as curb extensions, writing, “DDOT should develop a policy describing when curb extensions should be installed as part of retrofit projects,  rehabilitation projects, resurfacing projects, and new construction.  It is generally recommended that curb extensions be utilized to shorten crossing distances and to enhance the public space or to provide space for a bus shelter wherever possible on arterial roadways and at multi-legged intersections.”

Having no policy really complicated the debate over this 18th Street project. The original plan contained bulb-outs at most corners with on-street parking. Some residents and ANC commissioners loved the bulb-outs, while others raised concerns. Would these hinder delivery trucks, which generally double park at the corners? Would they be more dangerous for bicyclists? Are they even necessary?

Bulb-outs are a good design practice for pedestrian safety. And according to bicycle advocacy groups, they are not bad for bicycles, as long as they don’t block bicycle lanes or anything like that. In fact, by slowing traffic and forcing cars to turn carefully, they enhance safety. During the debates at community meetings and ANC meetings, though, I made these points, but DDOT generally did not. One ANC commissioner asked if DDOT could bring an expert in bulb-outs, to help differentiate those corners where they are valuable from those corners where they might prove a nuisance.

In the end, the ANC voted to approve bulb-outs along the commercial area, but reject them farther south. The DDOT project team promised to follow the ANC’s decisions. But the engineers must have felt bulb-outs were appropriate from the start, since they included them. It’s important to listen carefully to residents and neighborhood leaders, who can often point out specific local conditions that should bear on the project decisions. But choose to include or reject bulb-outs is too important a decision to leave entirely up to an ANC vote, especially when the ANC couldn’t get the information it wanted about bulb-out best practices to inform its own decision. It’s even less appropriate to leave it to the last resident who happens to bend the ear of the project team.

DDOT needs detailed policies on bulb-outs, turning radii, and other street design features. Those policies shouldn’t become straitjackets that prevent professionals from deviating from a design where it’s important, but neither should the designs depend simply on the luck of the draw for the project engineers, ANC commissioners, or vocal residents. When they do, as on 17th Street, each project ends up cutting feature after feature until we end up spending millions to change very little at all. Fortunately, on 18th, we ended up only cutting half of the changes. Hopefully the ANC made the right choice. Right now, we really don’t know.

David Alpert is the founder of Greater Greater Washington and its board president. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.