As evidence mounts, drumbeat for walkable streets grows

The evidence keeps piling up to support reform in street design and traffic engineering.

Recent research adds to volumes of studies that say walkable streets will make us safer, healthier, and improve the economy and communities.

As BCT reported last month, research by Chester Harvey at the University of Vermont examined the spatial characteristics of more than 7,400 miles of streetscapes in Boston, Baltimore, and New York City. Computer modeling determined the width of the streetscape, the street width to building height ratio, and tree canopy. Enclosed streets designed like “outdoor rooms” are more visually appealing and safer. “Crashes on smaller, more enclosed streetscapes were less likely to result in injury and death compared with larger, more open streetscapes,” Harvey reports in a paper to be presented to the Transportation Research Board in January of 2015.

A few weeks ago Richard Florida summarized a raft of new research showing that walkable places “not only raise housing prices but reduce crime, improve health, spur creativity, and encourage more civic engagement in our communities.” Some of this research is made possible by Walk Score, a website that assigns a walkability score for every address in the US.

Adding to the clamor is nationally known planner Jeff Speck, who in October made a compelling case for reducing lane widths in metro areas nationwide. This measure could save 900 lives a year among other benefits, he reports.

More walkability, streets like outdoor rooms, narrower travel lanes—what do these have in common? They are 180 degrees different from standard traffic engineering practice since the middle of the 20th Century.

High Walk Score is universally associated with historic street grids that do not meet modern street and engineering standards. The only recently built neighborhoods with high Walk Scores are new urban designs, modeled after old places. The growing admiration for high Walk Scores cannot forever co-exist with a transportation engineering profession that delivers low Walk Scores.

Harvey’s research is fascinating, because it negates the main thrust of modern street design: Move everything away from the street and give traffic plenty of room. Since at least the 1960s, US policy has promoted a 30-foot-clear zone on high volume streets. Have you seen an arterial road in the US built since the 1950s with a strong sense of enclosure? Wide open streets fronted by buffers and parking lots were built everywhere in the name of safety—but it’s hard to argue with a study of 7,400 miles of thoroughfares that contradicts the theory that wide open streets are the safest.

A study of 24 medium-sized California cities is also hard to challenge. Half of the cities are built with street grids, and the other half have modern suburban layouts. Norman Garrick and Wesley Marshall found in 2008 that the historic grids produce one-third of the traffic deaths per capita compared to the sprawling suburbs. That strength of association is impossible to explain in any way but this: The streets themselves are to blame.

Garrick, Marshall, and Daniel Piatkowski examined these same cities in 2014 and found that the historic grids are associated with lower obesity, blood pressure, and heart disease. One headline read “The Suburbs Made Us Fat.” This finding was backed up by Arizona State University researchers Emily Talen and Julia Koschinsky who found in October, 2014, that walkable places improve health, safety, and social relations.

And that's not all: The manuals that transportation engineers use overestimate traffic from new development by 55 percent, according to an article published this month in Access Magazine. Overestimates lead to overbuilt roads, less walking, more driving, and less sense of place.

How did the transportation planning and engineering professions go so wrong? In the Journal of the American Planning Association, Eric Dumbaugh of Florida Atlantic University explains how some tenets of modern street design grew out of conjecture, not science, that seemed reasonable at the time. Research that did not fit with the prevailing model was disregarded as aberration. This thinking was not questioned as long as US real estate markets and public opinion favored suburban expansion.

Now the market and public sentiment has shifted and new tools like Walk Score are breaking the foundations of conventional traffic engineering. After trillions of dollars invested, this must be embarrassing.

Transportation engineering is resistant to change, yet the drumbeat of reform is getting louder and more difficult to ignore.