Streetsblog Capitol Hill

It’s well-established that density and mixed-use development reduce driving. Right? But strategies like those don’t work the same way everywhere, according to new research published in the Journal of Transport and Land Use. While in major cities, denser development is linked to lower rates of driving, researchers found that in smaller cities it might not have much effect at all. The research suggests that for smaller cities, a focus on reducing block sizes and improving street connectivity may be the most effective way to cut down on driving, though the authors caution that more research is needed to draw universal conclusions.

According to new research, block sizes help explain why some people drive less than others in Norfolk, Virginia. Photo: Joey Sheely, Wikimedia

The research team, sponsored by the Federal Highway Administration, sought to drill down and identify how urban characteristics affect driving levels in different types of places. They looked at four different case studies: Seattle, WA; Richmond-Petersburg and Norfolk-Virginia Beach, VA (grouped together as one case study); Baltimore, MD; and Washington, DC. Using travel surveys and land use information, they modeled the impact on vehicle miles traveled (VMT) of five factors: residential density, employment density, mixed-use development, average block size (which they use as a stand-in for “measuring transit/walking friendliness”), and infill development (or distance to city center).

While the authors knew from previous research that these five factors all contributed to reducing VMT, they found that the Virginia regions didn’t follow the same patterns as the other three. In the smaller urban areas of Richmond-Petersburg and Norfolk-Virginia Beach, they found, mixed-use development did not have a significant impact on reducing driving.

“This is probably because in smaller urban areas, even those living in neighborhoods with well mixed land development may still need to travel far to reach work and non-work destinations,” the researchers write. “In other words, mixed development areas are less likely to be self-sufficient in smaller urban areas.” Mixing uses proved to be a good way to reduce driving in the larger metros.

These findings would seem to show a major weakness of New Urbanist-style “town centers” developed in otherwise suburban areas. A small walkable area isn’t enough to actually spark a real shift in transportation habits – the urban area has to be big enough that most people’s needs can be satisfied without a car. But lead researcher Lei Zhang said the findings don’t warrant that conclusion. “The paper has a small sample size,” Zhang said. “I wouldn’t want to generalize the results to other places.”

Zhang and his team are working on another paper that broadens the scope of their analysis to 20 urban areas. They hope this bigger data set will help planners evaluate land-use plans and how those decisions affect driving rates in different types of places.

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Matt Yglesias made an excellent point about NIMBYs over at Slate yesterday. Writing about opposition to multifamily residential construction in the tony neighborhood near Lake Calhoun in Minneapolis, Yglesias wondered how much value residents really place on keeping the area a “single-family residential community.”

The Alaskan Way Viaduct will cost 20 times more than drivers themselves will pay. So everyone else will pay instead.Image: WSDOT

Just because there’s value in something doesn’t mean people are willing to pay for it. Yglesias likens it to his third-generation iPad. “There would undeniably be a value in upgrading it to a fourth-generation iPad,” he says, but “it’s not worth what it would cost.”

So how much do the residents of Lake Calhoun value keeping their neighborhood single-family? Enough to let the entire rest of the city pay for it. But enough to pay for it themselves? Not a chance. Yglesias lays it out:

One thing [the] neighborhood group could do is look at the land they don’t want to see developed and buy it, thus leaving them free to do what they want with it. But they don’t want to do that, presumably because even though there’s “a value” in getting their way it’s less than the value of using the land for higher-density construction. What they want to do instead is get the city government to block the high-density construction, because that way the cost is spread across the entire population of Minneapolis in the form of foregone tax revenue.

The Minneapolis housing example reminds me of debates around the value of congestion-free roads. When roads are congested, many commuters jump to the “let’s build a wider road” approach, meaning all the taxpayers should pick up the tab to make their morning drive to work faster. But would these same commuters pay directly to speed their commute?

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Eschewing the faddish steps local governments sometimes take to retain and attract young professionals, Massachusetts has cut to the chase with a common-sense plan. Governor Deval Patrick is catalyzing walkable residential development as an official state policy in hopes of retaining young people by appealing to their needs and preferences.

Massachusetts is hoping to jumpstart walkable, transit-accessible residential development with a new set of incentives. Photo: Boston.com

Yesterday, Patrick announced a program called Compact Neighborhoods, which will provide incentives for the development of multi-family housing near transit centers. The Boston Globe reported that state officials hope the program will spur the creation of 10,000 new housing units annually. To be eligible for the incentive, developers will need to plan on at least eight units per acre for multi-family homes and four units per acre for single-family homes.

The announcement came after researchers and housing experts publicly made the case for a shift in housing to reflect changing demographic realities.

Barry Bluestone, director of the Kitty and Michael Dukakis Center for Urban and Regional Policy at Northeastern University, told the Globe that over the next eight years housing demand will be dominated by young families with significant debt and older people looking to downsize.

The new program is a step forward but may be just the beginning of what Massachusetts needs to meet demand for walkable neighborhoods. Harvard economist Ed Glaeser, an urbanist, said that he doubted 10,000 homes a year would be enough to meet demand.

“I think it is going to take stronger medicine,’’ he told the Globe.

It’s a pretty striking contrast, isn’t it? On the left, Florence, Italy, birthplace of the Renaissance. On the right, Atlanta, Georgia, home of the 23-lane freeway.

This was the central illustration in an illuminating discussion of how roads designed for high-speed car travel devour our landscapes and devastate their value. Steve Mouzon, principal at Miami’s Mouzon Design and author of The Original Green blog, argues in Better Cities and Towns that our fondness for wide, high-speed roads simply takes up too much space.

He compares Seaside, Florida, a community with a more traditional street pattern, with the landscape surrounding an interchange in Miami. In the former, 80.5 percent of the land is available for development; in the latter only 62 percent — an astonishing 34 percent of the land is consumed by roads.

Fast, highway-like roads hog land in four primary ways, Mouzon explains:

Curves — Increasing speed a little bit requires a big increase in the size of curves. At 20 miles per hour, any car can handle a curve with a 15-foot radius, so you’d think that tripling the speed would triple the radius, right? Wrong. At 60 miles per hour, curve radii are usually a few hundred feet, not the 45 feet you might guess.

Lane width — Faster roads need wider lanes. An eight-foot lane can handle 20 mile per hour traffic, but at highway speeds, you need 12 foot lanes [to give fast-moving drivers a wider berth].

Medians and shoulders — High-speed roads need wide medians and shoulders because a car can roll hundreds of feet beyond the point of collision or loss of control when it is traveling at highway speeds.

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