By Don Procter
What’s the best approach to suburban street layouts? A little of this and a little of that, suggests a Canadian planning team led by architect Fanis Grammenos, a senior researcher for the Canada Mortgage and Housing Corporation.
Following up on a three-year study of residential street patterns that concluded in 2000, the CMHC team has come up with a new suburban planning model that fuses the best traits of the traditional early 20th century street grid with the loops and cul-de-sacs of the modern suburb.
Following this model would improve livability while cutting suburban infrastructure and development costs by up to 30 percent, says Grammenos. It would also encourage 12 to 15 percent higher housing densities and provide more park and recreational space, he adds.
The CMHC model calls for new subdivisions to be divided into residential quadrants of roughly a quarter-mile square, a distance that can be crossed on foot in about five minutes. Within each quadrant, residential streets are laid out in a modified grid, what Grammenos calls a "variable function grid." Narrow, looped streets within the quadrants would reduce the speed and volume of vehicular traffic. The new pattern would also reduce nonresident through-traffic, he says.
The quadrants would be bounded by two collector streets and two arterials. Highest housing densities would be adjacent to arterial streets, intermediate densities adjacent to the collector streets, and moderate densities in the center. A continuous pedestrian footpath network would provide residents with several direct routes to public transit, retail, recreation, and services.
Grammenos says he views the arterials that border the residential areas as activity generators, zoned for commercial and service-related businesses. They represent an evolved main street or commercial strip, he says.
Grammenos says one of the largest land developers in the Canadian capital of Ottawa is talking about incorporating the VFG into a subdivision planned on the fringe of the city. The important thing now, he observes, is getting the message across to city planners and land developers.
For its open space model, the CMHC team looked at the 18th century plan of Savannah, Georgia, where open space is concentrated in squares at the center of 675-foot-square "wards." The squares function as virtual front lawns for many of the houses, and they are well-protected from heavy traffic because through-streets are located at the boundaries of each ward, just as is the case with the CMHC model.
Defending the cul-de-sac
It may surprise some planners to learn that the CMHC model includes loops and cul-de-sacs. Contrary to popular opinion, this curvilinear street pattern most associated with the modern suburb is more cost-efficient than the traditional street grid, Grammenos says. He notes that several studies conclude that loop and cul-de-sac patterns require 16 to 25 percent less land, while offering a higher degree of safety for children at play.
While recognizing the value of the grid system promoted by New Urbanists, Grammenos suggests its strongest advocates rely too much on 19th century planning principles. "We just can’t go back wholesale to the 19th century in order to solve contemporary issues of urban growth and subdivision planning," he says.
An earlier study by Grammenos for CMHC concluded that streets laid out in a grid pattern consume up to 50 percent more land than other layouts. At the same time, the study agreed with advocates that the grid does increase connectivity, "giving pedestrians the ability to reach their destinations as directly as possible." The study recommended a compromise: using open space — parks and squares — as connectors.
Don Procter is a writer in Toronto.
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