Major Intersection: Squaring the Circle

The illustration above depicts a wide, unsignalized intersection with a large, landscaped—but inaccessible—roundabout. Central medians divide the two-way traffic on both cross streets.

The large roundabout negates many of the benefits of a compact roundabout, such as managing speeds and reducing conflicts,  given the large turning radii and minimal level of deflection required for moving vehicles.

This intersection creates an unbalanced allocation of space between modes.

The central space is difficult to access due to high traffic volumes and a lack of pedestrian crossings.

Pedestrian crossings are inconsistent and recessed from the intersection, increasing walking distances.

Addis Ababa, Ethiopia. A very wide traffic circle where the central space is naccessible. Pedestrians have to cover very long distances in order to cross the street due to the wide diameter of the traffic circle. Sites like this present a great opportunity for redesign.

Ho Chi Minh City, Vietnam. A vulnerable user in a wheel chair tries to cross the street at a busy roundabout with no pedestrian crossings.

This reconstructions shows the transformation of a roundabout into an orthogonal configuration with signalized traffic control and a more balanced allocation of space between different modes.

Reduce lane widths and add dedicated transit lanes, protected cycle facilities, and an improved walking environment.

Reduce corner radii to limit the speed of turning vehicles. Reclaim these corners for additional pedestrian space and to shorten crossing distances.

 Align the number of travel lanes through the intersection. Mark skip lines to direct users on continuous paths.

Introduce dedicated, bidirectional transit facilities to reduce traffic congestion and increases total street capacity.

Ban turns that cross the transit lanes on unsignalized intersections.

 Take steps to activate wide central medians, which are valuable but underused public space. Use the wide median along the transit  corridor for transit shelters and stations. Design refuge spaces to align with pedestrian crossings, to provide access to stations, and  to offer seating opportunities recessed into landscape.

 A bidirectional cycle track is installed in the center median to create activity and utilize the space for mobility and recreational use.  The cycle track is continuous, with a protected center crossing and access to side-running cycle tracks on either street.

 Protect cyclists by adding corner refuge islands and forward stop bars that make them more visible to oncoming and turning vehicles.

Wide medians should be landscaped and planted to increase permeability, water infiltration, shade, and biodiversity.

Bogota, Colombia. A bidirectional bike lane in the central median.