tod news

Density is the key to sustainable cities
Alisha Newton | Vanderbilt Orbis


Macau (Flickr Creative Commons)

Macau, China is one of the world’s densest cities, with 44,183 people per square mile. Nearly half of the families in Macau live in dwellings that have an average of 180 square feet per person, which is about the size of a large bedroom. Because of their space-efficient lifestyles and their use of public transit, each resident of Macau citizen is responsible for roughly 3 metric tons of carbon emissions per year — one sixth of the carbon footprint of the average American.


True, it’s not fair to compare the city of Macau to the entire expanse of the United States. But even our densest city, New York, is half as dense as Macau, with 27,000 people per square mile, and we have dozens of other cities that are low-density and high-carbon. Take Nashville, Tennessee, one of the highest carbon-producing cities in the U.S.


Of course, Nashville is part of the southeastern United States, which suffers from the same set of carbon challenges, like historical dependency on coal for electricity. But Nashville looks bad even compared to other cities in the South. For example, Charlotte, North Carolina, is a peer city to Nashville based on the two cities’ population sizes and growth rates, but Charlotte is still much more energy-efficient.


The key difference lies in density: Music City has 1319 people per square mile, compared to Charlotte’s 2663 people per square mile. Fewer people per area means sprawl, and sprawl makes the city necessarily car-dependent. When people have to drive from home to workplace, the city consumes much more fuel.


“We have relied on personal vehicles in this city for the past 50 years, so our current infrastructure is designed for cars,” says Ron Yearwood, the Assistant Design Director at Nashville Civic Design Center (NCDC). “Most of the population of Davidson County — 80 to 85 percent — lives in single-family homes in suburban neighborhoods.” These areas are generally only accessible with cars, and there are no sidewalks, greenways, or public transit nodes, which are essential to the reducing Nashville’s carbon impact. To increase density in Nashville, “there is now multi-family housing going up,” says Yearwood, speaking of areas like 12 South and Aertson Midtown. “But we’re still behind our peer cities in terms of both transportation and residential options.”


One of those peer cities is Denver, Colorado, which has a successful public transit system and pedestrian network. Denver’s light rail serves an area with 2.8 million people, while the Nashville metropolitan area, including 13 of Tennessee’s fastest-growing counties, is predicted to have 2.6 million people by 2035.


If Nashville can build a well-designed public transportation system, then that predicted residential and commercial growth can happen along transit stops instead of extending the suburban sprawl. This so-called “transit-oriented development” (TOD) consists of residential communities built within half of a mile from a public transit stop. TOD gives urbanites independence from personal vehicles, reducing overall fuel emissions. To again cite Charlotte, the city began operating a 9.6-mile light rail called LYNX in October 2007. The Center for Transit-Oriented Development found that as of March 2011, LYNX had led to 930,000 square miles of commercial and residential development.


According to NCDC, the light rail and resulting development in Charlotte is a model of “strategic planning” for cities in the South. The city government builds public transit, and the private sector develops housing, and together the system effectively increases density. “If a city like Charlotte or Denver is successfully meeting its sustainability challenges, we want to find out what steps they took to get to where they are. We can then adapt their designs and policies to what already exists in Nashville.”


While the recent attempts to develop a light rail system in Nashville have been unsuccessful, Nashvillians do appear to support plans to build commercial centers with adjacent infill, according to the city government initiative Nashville Next. “We can densify existing land by turning empty stores and parking lots into mixed-use developments [infill] and small parks [greenfill],” affirms Yearwood. This approach to densification increases walkability, access to public transit, and property values.


“Our goal as urban planners in Nashville is to get people out of their cars and onto public sidewalks, greenways, and buses,” says Yearwood. Continued efforts to densify Nashville involve a 20-year plan for the mid-state area, created in conjunction with the Nashville Metropolitan Planning Organization and the Tennessee Department of Transportation. By 2035, Nashville residents could see a re-design of bridges, pikes, and sidewalks in order to increase walkability. In the meantime, however the sounds of construction echo from the future sites of bustling residential, restaurant, and retail centers all across town.