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Add Street-Connectivity Minimums into Subdivision Ordinances

Definition

Subdivision and zoning ordinances can establish a minimum level of street connectivity for future residential developments to create neighborhoods that are conducive to walking, bicycling, and transit use. Street connectivity consists of a road and/or path network that provides multiple routes and connections between destinations. It includes parallel routes, cross connections, many points of access, and short block lengths. Minimum standards of street connectivity can be based on maximum allowable lengths of blocks or by connectivity indexes of street links to intersections.

Benefits

  • Provides shorter, more direct routes between destinations, which encourages walking and cycling as a means of transportation
  • Reduces vehicle speeds
  • Reduces severity of accidents
  • Helps keep local trips on local streets rather than clogging arterial roads and highways
  • Provides route alternatives to drivers to avoid congestion and construction delays
  • Reduces travel distances as well as vehicle miles of travel
  • Improves both emergency access and response times
  • Allows for more efficient utility connections
  • Creates efficient trash and recycling routes
  • Facilitates bus-route and transit planning

Considerations

  • Public and developer education about the need for and benefits of frequent street connections
  • Developers may resist street connectivity requirements due to the potential decrease in developable land

Appropriate Contexts

  • Subdivision ordinances for new developments
  • Comprehensive Plan as the basis for future regulations
  • Zoning provisions

Professional Consensus

Examples

  • Franklin, TN
  • Cary, NC
  • Austin, TX
  • Portland, OR

Guidance

  • Street-connectivity standards for new developments often take the form of maximum allowable block length or an index based on the number of street links divided by the number of street nodes
  • Maximum-block-length determinations should factor in existing block dimensions, topography, and the desired scale, character, and connectivity the community aims to achieve. For example, in Portland, OR, the maximum block length is 530’; in Austin, TX, it’s 600’; and in Ft. Collins, CO, it’s 660’iMeck, Stuart; Morris, Marya; Kelly, Eric Damian; Bishop, Kirk. Model Smart Growth Codes, Interim Planning Advisory Service Report. Chicago: American Planning Association, 2006.
  • One-way streets operate best in pairs that are no more than a quarter-mile apartiPedestrian and Bicycle Information Center, 2004.
  • Align with existing local street grid to create four-way intersections
  • Introduce policies and practices to help keep travel speeds down
  • The Charlotte, NC, subdivision ordinance specifies:
    • Preferred street spacing ranges from 400’ to 600’ by context, requiring, say, three blocks for a 1,400 ft-wide property within a transit station area
    • No individual block face should exceed 1,000’ (with certain exceptions)
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