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Curb extensions are extensions of the curb line into the street, reallocating a portion of street space to pedestrians or ancillary uses.  Curb extensions are one of the most effective traffic calming tools, and can be used in a variety of ways, both at corners and mid-block.  They can mostly be found in residential neighborhoods and downtown commercial areas.  Also known as bulbouts, popouts, or neckdowns, curb extensions increase drivers' awareness of pedestrians, decrease crossing distance, reduce pedestrian exposure to traffic, and reduce traffic speeds. They are also referred to as neckdowns because they create a narrowing of the street at intersections or midblock.

Studies show curb extensions combined with a marked crosswalk increases yielding of vehicles to pedestrians waiting to cross the street. [1] Curb extensions also have a number of other purposes:

• Providing a prominent area for landscaping, public art, lighting fixtures, or freestanding A-frame signs.
• Providing an area for newspaper vending boxes. Cities or merchants sometimes want to remove vending boxes to de-clutter the sidewalk, but newspaper boxes are protected by the First Amendment to the U.S. Constitution, and must be accommodated. A large bulbout can provide a good compromise location.
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• Corner bulbouts carefully constructed to neckdown a street also eliminate high speed turning movements (particularly right turns), increasing safety for all users of the street.
• Providing protection for vehicles parked behind the bulbout. 
• Providing an area for street trees, other landscaping, or a groundwater recharge area, also known as a "bioswale".
  

 

 The Drainage Issue

An engineering challenge related to designing bulbouts is accounting for potential changes in water drainage patterns.  This can require completely rebuilding subterranean drain structures, at a cost of up to $50,000 per bulbout (2008 dollars), or avoiding disturbance of the curb.  A steel plank can be used to bridge between the curb and the bulbout structure, leaving water to flow beneath the plank (see photo).

 

ALSO ON THE LIVABLE STREETS NETWORK

• Streetsblog: Complete Streets Could Help America Lose Weight, Says CDC
  

• Streetfilms: Photos from Portland
  

REFERENCES

Each source is referred to by the same number every time it is cited. Please keep citation style consistent.

[1] Johnson, R. S. 2005. Pedestrian safety impacts of curb extensions: a case study. Federal Highway Administration Final Report SPR 304-321.

[2]

[3]

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PICTURE REFERENCES

[1] Corner curb extensions, Florida.  Photo by Dan Burden, Walkable Communities.

[2] Planter in curb extension. Photo by Dan Burden, Walkable Communities.

[3] Curb extensions and midblock raised crosswalk, Solana Beach, CA.  Photo by Dan Gallagher, WalkSanDiego.

FURTHER READING

• "Curb Extensions/Neckdowns." Context Sensitive Solutions.

KEYWORDS

bulbout, neckdown, crosswalk, landscaping, public art, context sensitive solutions, traffic calming, complete streets