May 2002
The Battle Over Dead Ends
By Ruth Knack, AICP
When it comes to stirring up neighborhood opposition, street connectivity ranks right up there with higher density. It’s really a red flag issue, says Kirk Bishop, a consultant with Duncan Associates in Chicago. People are afraid that more intersections will add noise, compromise their children’s safety, and lead to more crime.
A growing number of planners feel that connectivity is the answer to suburban traffic problems. Through streets disperse traffic, they say, in contrast to dead-end cul-de-sacs that pour cars onto arterials and make it virtually impossible to walk anywhere.
Within the last decade, communities across the country have revised their zoning ordinances and street standards to reflect this view. In 1993, for instance, Glendale, California, updated its street design standards to require that all existing streets be continued to connect with adjacent property. Similarly, the subdivision code of recently incorporated Wildwood, Missouri, requires that "streets normally shall connect with sheets already established or provide for future connections to adjoining unsubdivided tracts."
Several years ago, a city council member in Austin, Texas, became so frustrated with the design of unconnected subdivisions that she lobbied the city to commission a study of "connectivity ordinances" from two faculty members in the University of Texas department of community and regional planning. Associate professor Susan Handy, whose specialty is transportation planning and whose Berkeley Ph.D. thesis was on how urban design affects travel behavior, worked with colleague Bob Paterson to survey 11 locales.
They found two types of ordinances: the most common limits block lengths and restricts the use of cul-de-sacs. The other, more flexible type is based on a connectivity index, which in effect establishes performance standards. The index number is found by dividing the number of street links (connectors) by the number of street nodes (intersections). The communities studied were Boulder and Fort Collins, Colorado; Cary, Huntersville, and Cornelius, North Carolina; Middletown, Delaware; Orlando, Florida; and Portland, Beaverton, and Eugene, Oregon, along with Metro, the Portland-area regional government.
The study was completed two years ago, but the council never did pick up on its ideas, Handy says. "In part that’s because of strong resistance from developers, who didn’t want to be prevented from doing cul-de-sacs and required to put in more streets, which they thought would cost more."
This spring, Handy plans to begin an update of the survey, adding additional cities. The results will be published as an APA Planning Advisory Service report. One thing she will be looking at is interconnectivity. "A lot of the places are requiring a more gridlike network within subdivisions," she notes. "The trick is to connect with other developments."
Eugene, Oregon, one of Handy’s case studies, requires connectivity in all residential developments over half an acre, and limits local street block lengths to 600 feet. In a recent interview, Eugene planning director Jan Childs, AICP, noted that the local ordinance is based on the transportation goal of the statewide planning program.
In 1995, Eugene undertook a comprehensive overhaul of its street standards. "We were looking to not repeat the mistakes of the past and the one-size-fits-all approach. We looked at a variety of types of streets and said, ‘Here are some reasonable combinations.’ For example, for low-volume residential streets we said paving width should be able to vary, depend on whether there’s parking on one side, and so on.
"One of our biggest challenges was helping our fire department staff understand what we were trying to accomplish and at the same time to understand what their needs were. We followed the fire trucks on a tour of some of the older areas developed with narrow private streets, and then we talked about issues like paving width." The narrower widths were included in the local street plan, which was adopted in 1996.
Later, says Childs, the city also adopted code amendments that required street connections and limited block lengths to 600 feet and limited cul-de-sac lengths as well. "We did not feel we could ban cul-de-sacs," she says. "So far," she adds, the "standards are doing what we wanted. We have some narrower and more pedestrian-friendly streets."
Childs notes that California planner Peter Calthorpe was an influence on the Eugene standards. Long an advocate of connectivity, Calthorpe has now proposed a grander scheme, a new urban network, which is described in the story above.
Ruth Knack is the executive editor of Planning.