CURB EXTENSIONS Curb extensions (sometimes called “bulb-outs” or “neckdowns”) expand sidewalk space into the parking lane to narrow the street and provide additional space for people walking or crossing intersections. They also increase pedestrian visibility, shorten crossing distances, slow turning vehicles, and visually narrow the street. Curb extensions may also integrate green infrastructure elements such as planters in the pilot / interim design time interval and rain gardens in the more permanent state. While still completely useable, special consideration / design details are advised in areas subject to heavy snowfall.
DESIGN CONSIDERATIONS Curb extensions may be used at intersections or mid-block, on commercial or residential streets. The NACTO Urban Street Design Guide provides detailed information about design considerations for curb extensions in the following contexts: • • • •
Gateways Pinch points Chicanes Bus bulbs
Curb extensions are often used in areas with high pedestrian volumes. Demonstration or pilot/interim design curb extensions will be easiest to implement on streets that have curbside parking, and at intersections that already have a crosswalk in place. The length of a curb extension should at least be equal to the width of the existing crosswalk. The curb extension should generally be 1 - 2 ft. narrower than the parking lane. Include barrier elements to demarcate the curb extension from the existing street.
COMMON MATERIALS CATEGORIES 1
SURFACE TREATMENTS: Required striping (such as double solid white lines) serve to separate the curb extension space from the existing roadbed. Colored treatments can also be added - painted pavement, murals, or other specialized surface treatments such as epoxy gravel can be used to further define the space.
BARRIER ELEMENTS: Physical barriers (such as flexible delineators, granite blocks, or planters) should be used to define the place as a pedestrian-only zone.
LANDSCAPING ELEMENTS: Curb extensions provide an opportunity to integrate greening elements into the streetscape. In some cases, planters can also function as barrier elements.
SIGNS: The MUTCD provides guidance on required signs, which may include “pedestrian crossing” signs or stop signs. (Not shown.)
STREET FURNITURE: For large curb extensions that double as plaza space, seating and umbrellas may be a desirable amenity. (Not shown.)
6 94 · PROJECT APPLICATIONS
PROGRAMMING: For large curb extensions that double as plaza space, small scale programming can help activate the space. (Not shown.)
Photos illustrate the Baltimore Crossing project in Philadelphia, PA, led by the University City District For more info visit: universitycity.org
The only materials and design guidance for Tactical Urbanist demonstration, pilot, and interim design projects. Funded by the James L. Knigh...