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Water: Best Management Practices

Narrower Residential Streets

Minimum Measure: Post-Construction Stormwater Management in New Development and Redevelopment

Subcategory: Innovative BMPs for Site Plans
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Description

This better site design practice promotes the narrowing of streets to reduce the amount of impervious cover created by new residential development.  By doing so, stormwater runoff and associated pollutant loads may also be reduced. Currently, many communities require residential street widths of 32, 36, and even 40-feet. Wide streets provide two parking lanes and two moving lanes, but they provide more parking than is necessary. In many residential settings, street widths can be as narrow as 22 to 26-feet without sacrificing emergency access, on-street parking, or vehicular and pedestrian safety. Even narrower access streets or shared driveways can be used when only a handful of homes need to be served. However, developers often have little flexibility to design narrower streets because most communities require wide residential streets as a standard element of their local road and zoning standards. Revisions to current local road standards are often needed to promote a wider use of narrower residential streets.

Applicability

Narrower streets can be used in residential developments generating less than 500 or fewer average daily trips (ADT).  Such developments generally consist of 50 single family homes.  Narrower streets may also be feasible for streets generating 500 to 1,000 ADT.  However, narrower streets won't work for arterials, collectors, streets that carry greater traffic volumes, and those streets on which traffic volume varies over time.       

In most communities, existing local road standards will need to be modified to allow the use of narrower streets. Several communities have successfully implemented narrower streets, including Portland, OR; Bucks County, PA; Boulder, CO; and throughout New Jersey. In addition, there are numerous examples of communities where developers have successfully narrowed private streets within innovative subdivisions.

Siting and Design Conditions

Residential street design requires a balancing of competing objectives: design, speed, traffic volume, emergency access, parking, and safety. Communities that want to change their road standards to permit narrower streets need to involve all the stakeholders who influence street design in the revision process. Several excellent informational resources on narrow street design are provided at the end of this fact sheet.

Limitations

Real and perceived barriers hinder wider acceptance of narrower streets at local levels. Advocates for narrower streets need to respond to the concerns of local agencies and the general public. Some of the more frequent concerns about narrower streets are listed below.

  • Inadequate On-Street Parking. Recent research and local experience have demonstrated that narrow streets can adequately accommodate residential parking demand. A single family home typically requires 2 to 2.5 parking spaces. In most residential zones, this parking demand can be satisfied by one parking lane on the street and a driveway.
  • Car and Pedestrian Safety. Recent research indicates that narrow streets have lower accident rates than wide streets. Narrow streets tend to lower vehicle speeds and act as traffic calming devices. Furthermore, sidewalk access can be provided if needed.  Although this might add additional impervious area, net impervious area can be decreased due to greater reductions in street width. 
  • Emergency Access. When designed properly, narrower streets can easily accommodate fire trucks, ambulances, and other emergency vehicles.
  • Large Vehicles. Field tests have shown that school buses, garbage trucks, moving vans, and other large vehicles can generally safely negotiate narrower streets, even with cars parked on both sides. In regions with high snowfall, streets may need to be widened slightly to accommodate snowplows and other equipment.
  • Utility Corridors. It is often necessary to place utilities underneath the street rather than in the right of way.

In addition, local communities may lack the authority to change road standards when state agencies retain the review of public roads. In these cases, street narrowing can be accomplished only on private streets (i.e., maintained by residents rather than a local or state agency).

Maintenance Considerations

Narrower streets should slightly reduce road maintenance costs for local communities, since they present a smaller surface area to maintain and repair.

Effectiveness

Streets constitute 40 to 50 percent of impervious cover in residential developments.  Shifting to narrower streets can result in a 5 to 20 percent reduction in impervious area in typical residential subdivisions (Schueler, 1995).  Residential streets are a major source of sediment, bacteria, nutrients, hydrocarbons, metals and other stormwater pollutants (Bannerman, 1994).  Since nearly all pollutants on street surfaces and along curbs flow into storm drain systems during rainstorms, less imperviousness means less stormwater runoff and pollutant loadings.             

Cost Considerations

Narrower streets cost less to build than wider streets. The cost of paving a road averages $15 per square yard.  Shaving a mere four feet from existing streets can yield savings of more than $35,000 per mile of residential street. In addition, since narrower streets produce less impervious cover and runoff, additional savings can be realized in the reduced size and cost of downstream stormwater management facilities.

References

Bannerman, R. 1994. Sources of Pollutants in Wisconsin Stormwater. Wisconsin Dept. of Natural Resources. Milwaukee, WI.

Schueler, T.R. 1995.  Site Planning for Urban Stream Protection. Center for Watershed Protection, Ellicott City, MD.

Information Resources

American Association of State Highway and Transportation Officials (AASHTO). 1994. A Policy on Geometric Design of Highways and Streets. AASHTO Publications, Washington, DC.

Bucks County Planning Commission. 1980. Performance Streets: A Concept and Model Standards for Residential Streets. Doylestown, PA.

Center for Watershed Protection (CWP). 1998. Better Site Design: A Handbook for Changing Development Rules in Your Community. Ellicott City, MD.

Ewing, R. 1996. Best Development Practices: Doing the Right Thing and Making Money at the Same Time. American Planning Association, Planners Book Service. Chicago, IL.

Institute of Traffic Engineers. 1997. Traditional Neighborhood Development Street Design Guidelines. Washington, DC.

Local Government Commission. 2004. Free Resources. Accessed January 27, 2006.

Portland Office of Transportation. 1994. Report on New Standards for Residential Streets in Portland, Oregon. City of Portland, Portland, OR.

Urban Land Institute. Residential Streets. 2d ed. Washington, DC.


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