Most American cities have traffic congestion, and gasoline is expensive. People would drive less if the centers of cities were more developed, according to a 2010 analysis led by urban planner Reid Ewing of the University of Utah.
Reid Ewing: Almost any development at the center of a metropolitan area is better from a travel standpoint than having dense development on the fringe.
Ewing’s team analyzed the results of 60 previous studies to confirm that the number of miles people travel in their own vehicles is strongly related to the accessibility of the places they want to go, like jobs, schools and grocery stores.
Reid Ewing: Planners had been advocating the D’s – density, diversity, design – but they weren’t able to say just how much difference it would make in people’s driving, walking and transit use. And that’s what we did.
So accessibility of jobs, schools and stores – not just density of people – encourages less driving, according to this study. Ewing also said wide sidewalks and short blocks encourage people to go places on foot more often. He said that over the past 30 years, urban planners have been shifting the dominant model of development from auto-focused cities to more walkable cities.
Reid Ewing: People will generally see a more livable urban environment, one where you want to be on foot, rather than one where you’re only comfortable being in your car.
Ewing said many people are concerned that the large number of vehicles on American roads creates local air pollution, contributes greenhouse gases to climate change, and decreases quality of life with time-consuming commutes. Urban congestion is getting worse every year, he said, and prior studies suggest that building more roads doesn’t help.
Reid Ewing: We now know that we can’t pave our way out of congestion, so we have to reduce the amount of driving people do.
As urban sprawl continues, he said, urban planners are looking at how factors like density, the diversity of uses in a development, and street design affect how much people use their cars. Ewing explained what are called the five D’s.
Reid Ewing: Density is the first factor that comes to mind, but it’s not necessarily the most important. Holding other things constant, the amount of driving we do declines with the density of development. Diversity of land uses is a second factor. Rather than segregating residential from commercial land uses, keep them close together. Design is the third – how streets are laid out, whether they are interconnected on a grid or disconnected with lots of dead ends. The fourth D is destination accessibility – how central are developments within the region. The closer to downtown typically, the better. Finally, the fifth D is distance to transit. We try to keep it within a quarter of a mile or less.
Learning to love science. As a producer for EarthSky, Lindsay Patterson interviews some of the world's most fascinating scientists. Through EarthSky, her work content is syndicated on some of the world's top media websites, including USAToday.com and Reuters.com. Patterson is also charged with helping to stay in steady communication with the thousands of scientists who contribute to EarthSky's work of making the voice of science heard in a noisy world. She graduated from Colorado College with a degree in creative writing, and a keen interest in all forms of journalism and media.