Global Street Design Guide

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Global Street Design Guide

Complex Intersection: Adding Public Plazas

Complex intersections, especially those situated in busy commercial areas or at the junction of several streets, have tremendous potential to fulfill latent demand for public space. Non-orthogonal intersections are common in irregular and spontaneous urban fabrics and when two or more orthogonal grids meet. Lacking legibility, these intersections present safety hazards to all users.

Existing Conditions

This illustration depicts a large, signalized, complex intersection. Traffic volumes and multi-phase signals result in long delays and confusion among all users.

Acute-angled intersections reduce visibility for motorists, while obtuse intersections allow for high-speed turns and unnecessarily long pedestrian crossings.

Here, a major street intersects with two smaller streets and a diagonal street, creating a residual space that becomes de-facto parking.

The complex geometry results in long and recessed crossings, making it difficult for all users to navigate the intersection.

Before: São Paulo, Brazil.

After: São Paulo, Brazil.

Design Guidance

The intersection is transformed by simplifying and prioritizing the orthogonal geometry, adding public space, and changing the  function of smaller streets.

Redesign intersections to be as close to 90 degrees as possible, implementing turn restrictions and street reversals where  applicable.

Prioritize the primary street and use curb extensions on the diagonal streets to facilitate a perpendicular intersection.

Simplify the geometry and reduce the number of streets intersecting simultaneously, to eliminate the need for multi-phase signalization.

Plan signal timing to align concurrent and non-conflicting movements that reduce phases and cumulative cycle length, improving operational efficiency.

 Convert the residual space into a pedestrian plaza. Work with local businesses and residents to program, manage, and maintain the newly created public space. See: Pedestrian Plazas.

 Reorganize curbside parking and recess it from the intersection.

 Consider the transformation of one of the small streets into a pedestrian space or a shared space to further simplify the intersection and improve vibrancy of the area. Add a raised crossing and a pedestrian refuge island to provide a safer crossing and direct access to the new pedestrian-priority street.

Align curb extensions, pedestrian refuge islands, and pedestrian crossings with sidewalks to reduce crossing distances and increase pedestrian safety and convenience.

Mark conflict zones for cycle facilities through the intersection and plan Advanced Stop Bars. See: Designing for Cyclists.

Cyclists are more exposed in obtuse and ambiguous intersections, so conflict markings must be prominent and may be supplemented by leading cycle intervals to improve safety.

Buenos Aires, Argentina

Adapted by Global Street Design Guide published by Island Press.

Complex Intersection: Improving Traffic Circles

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Complex Intersection: Improving Traffic Circles