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Urban Street Design Guide Index

Urban Street Design Guide
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Sidewalks

Sidewalks

Sidewalks play a vital role in city life. As conduits for pedestrian movement and access, they enhance connectivity and promote walking. As public spaces, sidewalks serve as the front steps to the city, activating streets socially and economically. Safe, accessible, and well-maintained sidewalks are a fundamental and necessary investment for cities, and have been found to enhance general public health and maximize social capital.

Just as roadway expansions and improvements have historically enhanced travel for motorists, superior sidewalk design can encourage walking by making it more attractive.

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The sidewalk is the area where people interface with one another and with businesses most directly in an urban environment.

Sidewalk Zones

Frontage Zone

1 The frontage zone describes the section of the sidewalk that functions as an extension of the building, whether through entryways and doors or sidewalk cafes and sandwich boards. The frontage zone consists of both the structure and the facade of the building fronting the street, as well as the space immediately adjacent to the building.

Pedestrian Through Zone

2 The pedestrian through zone is the primary, accessible pathway that runs parallel to the street. The through zone ensures that pedestrians have a safe and adequate place to walk and should be 5–7 feet wide in residential settings and 8–12 feet wide in downtown or commercial areas.

Street Furniture/Curb Zone

3 The street furniture zone is defined as the section of the sidewalk between the curb and the through zone in which street furniture and amenities, such as lighting, benches, newspaper kiosks, utility poles, tree pits, and bicycle parking are provided. The street furniture zone may also consist of green infrastructure elements, such as rain gardens or flow-through planters.

Enhancement/Buffer Zone

4 The enhancement/buffer zone is the space immediately next to the sidewalk that may consist of a variety of different elements. These include curb extensions, parklets, stormwater management features, parking, bike racks, bike share stations, and curbside bike lanes or cycle tracks.

Sidewalk Design

Discussion

Sidewalks are an essential component of the urban environment and serve as key corridors for people, goods, and commerce. In accordance with ADA accessibility guidelines, sidewalks should be provided on all streets in urban areas.3
Numerous studies have shown that good pedestrian network connectivity and walkability have a positive impact on land values.4
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"Walkability is strongly associated with higher housing values in nearly all metropolitan areas. The choice, convenience and variety of walkable neighborhoods are reflected in housing markets and are the product of consumer demand for these attributes. The nation’s urban leaders should pay close attention to walkability as a key measure of urban vitality and as impetus for public policy that will increase overall property values – a key source of individual wealth and of revenues for cash-strapped governments in a tough economy." - Joe Cortright, Walking the Walk: How Walkability Raises Housing Values in U.S. Cities (Chicago: CEOs for Cities, 2009), 3.
Sidewalks have significant lifespans and can be maintained without replacement for 25 years or more, depending on the context.5

Critical

Sidewalks have a desired minimum through zone of 6 feet and an absolute minimum of 5 feet. Where a sidewalk is directly adjacent to moving traffic, the desired minimum is 8 feet, providing a minimum 2-foot buffer for street furniture and utilities.6
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Sidewalk design should go beyond the bare minimums in both width and amenities. Pedestrians and businesses thrive where sidewalks have been designed at an appropriate scale, with sufficient lighting, shade, and street-level activity. These considerations are especially important for streets with higher traffic speeds and volumes, where pedestrians may otherwise feel unsafe and avoid walking.
Sidewalks should be provided on both sides of all streets in all urban areas. On shared streets, the street itself serves as the path of travel and should be designed in accordance with accessibility recommendations outlined in the shared street section of these guidelines. In certain instances, such as on more rural or suburban roads connecting urban areas, it may be advantageous to build a shared-use path adjacent to the main roadway as a substitute for a sidewalk. In this case, the shared use path should meet the general criteria to serve adequately as a sidewalk or pathway.
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Boulder, CO has a regional network of multi-use paths which run alongside major highways and arteries.
The use of shoulders as a substitute for sidewalks is never justified in urban areas. Sidewalks should be delineated by a vertical and horizontal separation from moving traffic to provide an adequate buffer space and a sense of safety for pedestrians. Wide low-volume local or residential roads without sidewalks should be upgraded, but in the interim may be regulated as shared spaces or improved through the use of temporary materials where there is a potential danger to pedestrians.
Sidewalk design may be compromised by roadside design guidance that requires lateral offsets or clear zones forgiving to higher vehicle speeds. Use a lower design speed or widen the sidewalk to mitigate these impacts.
Delineation of a strict clear zone or minimum offset is not a required feature in urban environments. For the purpose of maintenance, cities should evaluate the impact of street trees, signs, and other elements on the structural integrity of the curb and access needs for parked vehicles or loading/unloading.
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For more information on clear zones in urban areas, see "Design of Safe Urban Roadsides: An Empirical Analysis" by Eric Dumbaugh. Transportation Research Record: Journal of the Transportation Research Board, No. 1961, Transportation Research Board of the National Academies, Washington, D.C., 2006, pp. 74–82.
Where transit stops are provided, bus shelters should be placed at the left or right edge of the walkway, but never directly within the path of travel. Where insufficient space exists, consider the application of a bus bulb.
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Relocation of fixed objects, such as utility poles, light fixtures, and other street furniture should not impinge on or restrict the adjacent walkway. Walkways must be clear of fixed objects in coordination with ADA accessibility guidelines.7
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Ensure that sidewalks are without major gaps or deformities that would make them non-traversable for wheel- chairs and other mobility devices.
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At driveways, sidewalks should be maintained at-grade through the conflict zone.
Any construction project that obstructs the sidewalk should be mitigated through the provision of a temporary sidewalk that affords a safe and convenient passage or clearly directs users to an equivalent nearby detour.
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Recommended

Façades and storefronts should be designed to cater to the eye level of pedestrians.

Strategies include:

  • Lighting scaled to the pedestrian realm in addition to overhead lighting for vehicles.
  • Benches and other seating platforms designed into the structure itself or placed within the frontage zone.
  • Incentives to provide awnings, sidewalk cafes, and other elements that improve the comfort and appearance of the sidewalk.
  • Where security concerns are present, use of permeable, rather than closed, metal shutters on storefronts at night (above).
  • Provision of adequate lighting beneath scaffolding and other construction sites.
Select street trees and tree wells whose roots have a limited impact on the integrity of the sidewalk’s structure.
Sidewalk cafes foster street life and have the potential to increase business along a corridor. Where provided, sidewalk cafes should not impinge upon the accessible pedestrian pathway.
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For more information, see "Greenway Cafe Guidelines." Boston Redevelopment Authority, 2007.
Where a city decides to repurpose a portion of the sidewalk as a raised bikeway, utilities and other street furniture should be relocated (in the facility’s permanent reconstruction) to adequately separate pedestrian and bicycle traffic.
If a sidewalk is directly adjacent to the roadway, 2 feet should be added to the absolute minimum clear path width to ensure that there is sufficient space for roadside hardware and snow storage.8 Parking provides a valuable buffer between the pedestrian and vehicle realm. Urban arterials or high- volume downtown streets directly abutting the pedestrian realm should be buffered in some capacity, whether through a street furniture zone, parking, cycle track, or other feature. Sidewalks of minimum dimensions directly adjacent to the traveled way should be avoided.
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When pedestrian networks cross municipal boundaries, efforts should be made to ensure seamless continuity of the pedestrian infrastructure.

Optional

In newer residential areas, many streets have been constructed without sidewalks. If traffic volumes are sufficiently low in these areas, consider designating or upgrading these areas to shared streets. This requires the addition of specific traffic calming devices and regulations that offset potential conflicts with traffic accessing local properties.
Many older residential areas have trees whose roots have compromised the integrity of the sidewalk. On low-volume roads, consider the application of a curb extension that obviates the need to remove trees or the installation of a wider sidewalk during reconstruction.
Where pedestrian volumes create congested conditions along sidewalks, cities are encouraged to pursue temporary means to ease overflow from the sidewalk onto the streets. Interim elements, such as epoxied gravel pavements or temporary lane closures, may be able to provide an interim solution until a city can widen the walkway. If special events are anticipated to significantly increase pedestrian traffic, similar strategies should be pursued to ensure pedestrians are not forced into vehicular traffic.

See Interim Design Strategies

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Lane closures should be considered to ease sidewalk congestion during times with known high pedestrian volumes.

Street Trees

Street trees enhance city streets both functionally and aesthetically. Trees provide shade to homes, businesses, and pedestrians. Street trees also have the potential to slow traffic speeds, especially when placed on a curb extension in line with on-street parking, and may increase pavement life by avoiding extreme heat. Aesthetically, street trees frame the street and the sidewalk as discrete public realms, enriching each with a sense of rhythm and human scale.

Requirements for tree spacing depend upon a number of key factors and should be tailored to the chosen species, standard (or desired) tree pit size, fixed property lines, setback from curb, and integration with street lights and other furniture.

Street trees may be removed to satisfy sight distance or clear zone requirements only in extreme cases, where the installation of traffic control devices has been precluded. Larger trees protect pedestrians from errant vehicles.

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For more information, see "Street Trees and Intersection Safety," by Elizabeth McDonald et al. http://www.uctc.net/papers/768.pdf.

Clear Zones

Clear zones are applicable on rural highways with high vehicle speeds, not in urban areas.

The concept of “clear zones” is sometimes cited in the highway design process. A clear zone represents an unobstructed, traversable area beyond the traveled way, often a paved or planted shoulder or a short setback on the sidewalk.9 Clear zones provide a run-off zone for errant vehicles that have deviated from the main roadway and are intended to decrease the frequency and severity of fixed-object roadside crashes, forgiving driver error.10

See Design Speed

While clear zones are applicable as a safety parameter for the Interstate and freeway system, in urban settings, delineation of a minimum set back from the curb is not a required element. To the greatest extent possible, the lateral distance between the traveled way and the sidewalk (or parking lane) should be minimized, providing ample space for sidewalks and other amenities.11

Removal of roadside impediments (trees, street furniture, etc.) has an ambiguous safety record in urban environments and is at odds with city policies striving to increase pedestrian traffic and spur economic activity. Street trees and other roadside features are superior to wide shoulders or run-off zones, as they can decrease overall speeds and encourage a more pedestrian-friendly environment.

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For more information on clear zones in urban areas, see "Design of Safe Urban Roadsides: An Empirical Analysis" by Eric Dumbaugh. Transportation Research Record: Journal of the Transportation Research Board, No. 1961, Transportation Research Board of the National Academies, Washington, D.C., 2006, pp. 74–82.

Footnotes

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  1. A 2003 newsletter of “Let’s Talk Business” cited several economic benefits of walkable communities, including a case study from Lodi, CA that cited how pedestrian improvements paired with economic development incentives dropped the retail vacancy rate from 18% to 6% and also resulted in a 30% increase in downtown sales tax revenues.

    Bill Ryan, “Let’s Talk Business: Ideas for Expanding Retails and Services in Your Community,” UW Extension, July 2003.

    A 2011 research study titled Examining Walkability and Social Capital as Indicators of Quality of Life at the Municipal and Neighborhood Scales used a case study approach between three communities in New Hampshire. Comparisons between the more walkable and less walkable neighborhoods show that levels of social capital are higher in more walkable neighborhoods.

    Shannon H. Rogers, John M. Halstead, Kevin M. Gardner, and Cynthia H. Carlson, “Examining Walkability and Social Capital as Indicators of Quality of Life at the Municipal and Neighborhood Scales,” Applied Research Quality of Life 6 (2010): 201–213.

  2. Examples of higher standards for sidewalks include downtown Washington, D.C. (16 foot + 6 foot buffer), Chicago (varies between 10–12 feet depending on context), San Francisco (9–17 feet depending on context), Boston (target varies, but minimum is 7 feet for several street types).
  3. As an example, Washington, D.C.’s Design Engineering Manual states that a sidewalk should exist on both sides of every street or roadway.

    Design and Engineering Manual (Washington, D.C.: D.C. Department of Transportation, 2009): 29–3.

  4. Joe Cortright, Walking the Walk: How Walkability Raises Housing Values in U.S. Cities (Chicago: CEOs for Cities, 2009).
  5. Paul D. Thompson, Kevin M. Ford, Arman Mohammad, Samuel Labi, Arun Shirolé, and Kumares Siuha. NCHRP Report 713: Estimating Life Expectancies of Highway Assets. Volume 1: Guidebook. (Washington, D.C.: Transportation Research Board, 2012).
  6. Federal Highway Administration, “Sidewalk Corridor Width,” Designing Sidewalks and Trails for Access (Washington, D.C.: FHWA, 2001).
  7. According to the American Disabilities Act, the minimum sidewalk width at bus stop loading points should be 8 feet to ensure clear boarding and alighting. The location of a bus shelter, bench, or other permanent fixtures should ensure a 3-foot clear path for pedestrian travel. However, 3 feet is not the recommended width for sidewalks, it is the absolute minimum needed to ensure a clear path of travel when obstacles exist in the sidewalk.

    Americans With Disabilities Act of 1990.

  8. “Where sidewalks are placed adjacent to the curb, the widths should be approximately 6 m [2 ft.] wider than the minimum required width. This additional width provides space for roadside hardware and snow storage outside the width needed by pedestrians.”

    A Policy on Geometric Design of Highways and Streets, 4th Edition (Washington, D.C.: AASHTO, 2001).

  9. AASHTO’s Roadside Design Guide defines a “clear zone as the total roadside border area, starting at the edge of the traveled way, available for safe use by errant vehicles. This area may consist of a shoulder, a recoverable slope, a non-recoverable slope, and/or a clear run-out area.”

    Roadside Design Guide, 4th Edition (Washington, D.C.: AASHTO, 2011).

  10. In urban areas, the presence of fixed roadside objects (such as trees) is correlated with lower crash frequencies. This suggests that roadside objects in urban areas may actually enhance safety (by increasing driver caution and reducing speeds). As referenced in Eric Dumbaugh, “Safe Streets, Livable Streets,” Journal of the American Planning Association 71 (2005): 295.
  11. The AASHTO Green Book suggests a minimum offset distance of 1.5 feet between the face of the curb to the nearest fixed object off the roadway.

    A Policy on Geometric Design of Highways and Streets, 4th Edition (Washington, D.C.: AASHTO, 2001).

References

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Adapted from the Urban Street Design Guide, published by Island Press.

References

References for Sidewalks: 22 found.