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Bicycles/Pedestrians

Safety Toolbox: Engineering


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Curb extensions: bulb-outs and chokers



   
The sidewalk extends across the parking lanes to the edge of the travel lanes to narrow the distance of the road that a pedestrian has to cross.
objective To improve the visibility of pedestrians waiting to cross by bringing them closer to the center of the driver's cone of vision and by minimizing the impact of parked vehicles on pedestrian visibility.
applications This treatment is used in areas with high pedestrian activity where there is a need to shorten crossing distances and improve the visibility of pedestrians. Landscaping is required to guide visually impaired persons to the crossing. Curb extensions are only appropriate where there is an on-street parking lane.
target population All Pedestrians, Motorists
crash type Pedestrian R/W Violation-Intersection, Excessive Speeds, Pedestrian Violation-Intersection
advantages
  • Reduces the distance that pedestrians travel in the street and the potential for being struck by a vehicle.
  • Adds sidewalk space for the installation of a curb ramp in a narrow sidewalk.
  • Helps slow the speed of turning vehicles by tightening up the corner radius.
  • Improves the visibility of pedestrians by placing them where drivers can see them, where parked vehicles do not obscure their presence.
  • Makes it very difficult for drivers to park illegally at the corners of intersections.
  • Has significant traffic-calming effects.
disadvantages
  • Can be a fixed object itself that drivers may run into at night and in inclement weather conditions such as snow unless adequate on-street parking is immediately adjacent
  • No buffer between the pedestrian waiting at the curb and the passing vehicles.
  • Can pose obstacles to street sweepers and snowplows.
  • Requires landscaping to guide pedestrians with visual impairments to crosswalks.
  • Loss of on-street parking.
  • Can create drainage problems or trash accumulation
  • Increases the potential for conflicts between bicyclists and motorists.
  • Impacts on the turning ability of trucks and other heavy vehicles.
pointers Curb extensions should not extend farther than parked cars or striped shoulders into the travel lane in order to avoid conflicts with bicycles.
cost Medium to High, $2,000 - $25,000 average per extension, depending on the need to modify drainage. If patterned concrete and other street furniture are included, costs can increase significantly.
responsibility Public Works Department, Planning Department
further reading

Ewing, R. Traffic Calming, State of the Practice. Report no. FHWA-RD-135. Washington, DC: ITE under contract with US DOT, FHWA, 1999

Canadian Guide to Neighborhood Traffic Calming. Ottawa, Ontario:  Transportation Association of Canada, December 1998.
examples Walk Boston, Boston; City of Boston, MA; City of Philadelphia, PA; City of San Francisco, CA
related tools Pedestrian Refuge Islands; Chicanes

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