By Dom Nozzi
Economists use a term—The Barrier Effect—that has become crucial for smart growth transportation and community planners to understand in the context of community and transportation design.
The Barrier Effect (Litman, 2002), when applied to transportation planning, refers to the “barriers” that over-design for car travel creates for other forms of travel. To put it simply, designing an “incomplete” street (a street that is designed exclusively or predominately for cars) makes travel by walking, bicycling and transit more difficult. In effect, an incomplete street creates a self-perpetuating vicious cycle because the travel barriers they create tend to continuously recruit new motorists who were formerly non-motorists—non-motorists who now find that on the incomplete street, travel by walking, bicycling or transit is unacceptably unsafe, inconvenient or otherwise unattractive.
Over time, the incomplete street increases the proportion of community members who are now traveling by car. Tragically, this on-going recruitment of new motorists compels many communities to spend large sums of public dollars to widen and speed up roads to (unsuccessfully) strive to accommodate the growing number of motorists. And these newly widened, higher speed roads create an even larger barrier effect. Which recruits even more motorists, which then builds pressure for even wider roads.
Disastrously, conditions that create a high quality of life for people are strongly at odds with the conditions needed to enable convenient, high-speed, free-flowing car travel. Most of us enjoy compact, walkable, lower-speed, human-scaled neighborhood design. Cars, by stark contrast, are happiest with gargantuan, high-speed roads and parking lots, bright lights, and unwalkable dispersion of land uses. Because of the barrier effect found on incomplete streets, citizens are compelled to urge that conditions be improved for car travel. The unintended consequence is a citizenry that presses for conditions that actually reduce their quality of life. On incomplete streets, then, citizens become their own worst enemy.
The barrier effect therefore becomes an endless, ruinous, bankrupting process.
Fortunately, a growing number of communities throughout the nation have recognized the toxicity of incomplete streets, and are smartly starting to reverse this downwardly spiraling process by calling for complete streets (Wikipedia, 2007). Streets that are designed, to the extent possible and appropriate, to accommodate all forms of travel. A street that is rich in transportation choice.
Complete streets have a number of beneficial influences over how a community develops over time.
Formerly incomplete streets that have been transformed into complete streets can expect to see adjacent land uses evolve into more complete communities. Car-only incomplete streets tend to result in the replacement of residences and locally-owned shops with strip commercial development and national Big Box chain stores. When converted to complete streets, adjacent land uses also become more “complete.” Instead of “Anywhere USA” franchise architecture that nearly inevitably feeds on car-only regional traffic volumes, complete streets are comparatively more livable—and lovable. By being more hospitable, complete streets induce the return of residential land uses. Instead of a monolith of commercial, warehouse and industrial uses (the only uses that can tolerate inhospitably incomplete streets), complete streets tend to attract a complete set of community types: shops, offices, civic, and residential.
With a more diverse, complete land use pattern, trip distances become shorter, which creates a self-perpetuating virtuous cycle, because shorter trip distances make walking, bicycling and transit use more practical, safe and pleasant.
Not only does the complete street create more complete land uses, but it also draws and retains a more diverse population. This is due to the fact that by creating more transportation choices, the complete street makes the adjacent residential housing more affordable. More affordable because households are able to own fewer household cars, which is a dramatic, effective way of creating affordability (because significantly less household dollars are thereby devoted to car ownership).
Complete streets tend to support adjacent populations that are also more diverse and equitable. A large number of citizens do not drive, such as children, a portion of the disabled population, and seniors. (About a third of the national population does not drive a car. See Wikipedia, 2007). In America, losing the ability to drive a car typically means facing the inconvenient indignity of losing travel independence. Loss of travel independence is particularly acute with incomplete streets. When the street is complete, those citizens who do not drive a car are now more able to live near the street, because the complete street better supports pedestrians, bicyclists, the disabled, and transit users.
The higher quality of life provided to adjacent land uses by the complete street increases property values and draws a broader mix of income groups.
Investment in property adjacent to a complete street becomes more likely because development near a complete street tends to be more stable, predictable and context-sensitive. The unpredictable nature of development along incomplete streets makes investment more risky and therefore less likely.
In sum, the complete street results in an adjacent land use pattern that is more diverse, sustainable, equitable, higher value for residential, safer and more local.
The higher quality of life and place-making delivered by complete streets and complete communities induces higher levels of civic pride, and provide a powerful, sustainable economic engine for the community.
Litman, Todd. (2002). “Evaluating Nonmotorized Transport.” TDM Encyclopedia. Victoria Transport Policy Institute.
Wikipedia. (2007). http://en.wikipedia.org/wiki/Complete_streets
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Or email me at: dom[AT]walkablestreets.com
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