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Guest Post: Active Healthy Cities Are a Key to Success

Editor’s Note: Below is a guest blog post from James F. Sallis, Ph.D., Professor Emeritus, UC San Diego Department of Family Medicine and Public Health


Active Healthy Cities Are a Key to Success

I have spent the last 20 years doing research about what makes for an active healthy city. Our teams have done this research based at both UC San Diego and San Diego State University. We have learned a great deal that is relevant as leaders plan the future of San Diego County.

Research results

My main research interest is improving health through physical activity, which accounts for about 10% of deaths and 10% of health care costs in the US. As almost everyone knows, being active is one of the most important ways to reduce risk of many chronic diseases and improve mental health. Our work on active cities started with the city planning concept of neighborhood walkability, which allows residents to easily walk to shops, services, jobs, and schools. We identified neighborhoods in several parts of the country that were high and low in walkability, then recruited residents from those neighborhoods and measured their physical activity, height, and weight. We conducted separate studies with children, adolescents, adults, and older adults.

In all age groups, people who lived in high-walkable neighborhoods did more total physical activity than those in low-walkable areas, measured by electronic devices, and much more walking for transportation. Further, residents of high-walkable neighborhoods were less likely to be overweight or obese in all age groups except adolescents. The effects are meaningful. For adults, the physical activity difference between high- and low-walkable neighborhood residents could theoretically translate into 3 fewer pounds gained per year. Reinforcing this finding, overweight/obesity rates were 60% in low-walkable and 48% in high-walkable neighborhoods.

Based on our own studies and hundreds of others, I have become convinced that high-walkable neighborhoods are generally healthier. The US Surgeon General, Centers for Disease Control and Prevention, National Academy of Medicine, and World Health Organization all agree.

What is walkability?

But what makes a neighborhood walkable? Walkability has 3 core components: mixed land use, highly-connected streets, and higher residential density.  In mixed land use, residences are inter-mingled with other uses, so shops, services, jobs, and schools are within walking distance. The opposite is separation of uses, defined by zoning, which puts daily destinations beyond walking distance for most people. Separation of uses is a key reason over 90% of all trips in San Diego County are by car. Connected street networks are usually a grid pattern that provides direct routes for walkers. The opposite pattern is winding streets with few intersections we see in the suburbs that make walking distances longer than they need to be. High residential density contributes to walkability by making it possible to have enough people to support local shops, services, and public transit.

I am pleased the San Diego City Council recently voted unanimously to approve a mixed-use zoning code. This is good news that will contribute to achieving the goals of Circulate San Diego. My main disappointment is it took so long to “legalize” mixed use. My preference would be for mixed use zoning to be the default, with strong justification needed for separate use zoning.

Do people want walkable neighborhoods?

I am very aware that higher residential density is treated as a 4-letter word and routinely attracts strident opposition throughout the County. I understand nobody wants their quiet neighborhood to turn into Manhattan, but of course nobody is proposing that. The argument I hear most often is that more density leads to more traffic congestion. That could be true when the only change is increased density, but there are other aspects to consider. Low density, single-family-home neighborhoods are built for car travel and create dependence on cars. In low-walkable neighborhoods, walking is not an option due to distance, and bicycling is dangerous. High-frequency public transit is not feasible in low-walkable neighborhoods because the distances are too large and the riders are too few. Thus, the solutions to car-dependence and traffic congestion are more mixed use areas so people can walk for daily needs and higher density so good transit service gives people viable options. Then transportation options need to shift from only building roads to supporting active transportation with better sidewalks, protected bike paths, and vastly expanded public transit.

Though we mostly hear objections to the components of walkability, our research tells a different story. We found that higher scores on all the components of walkability were correlated with higher neighborhood satisfaction. People also liked their neighborhoods better when there were well-designed sidewalks, safe street crossings, nearby parks, and nearby public transit. Other research shows that demand for walkable neighborhoods is much higher than supply, especially among older adults and millennials, who do not want to be forced to drive everywhere. Decades of separate use zoning meant it was illegal to build the healthy walkable communities many or most people wanted.

Active design may be the key to successful cities

Our group examined the scientific literature to see if there were other benefits of designing parks and trails, neighborhoods, transportation facilities, and schools for physical activity. For all of these elements of cities “active design” was related to better physical and mental health, less air pollution, and fewer carbon emissions. Thus, “active cities” could help us reduce health care costs and meet our climate action goals. Of special interest to city leaders, active design was related to better economic performance, and benefits accrued to many stakeholders. Parks, trails, sidewalks, and street trees increase property values. Retail shops in walkable areas are more profitable per square foot. The value of homes is higher in walkable areas and declined less during the Great Recession. It costs cities less to build and maintain water and sewer infrastructure in walkable neighborhoods because the distances are less. Our surprising conclusion was active cities may be the key to prosperous cities.

Let’s advocate for complete communities

Based on the past 20 years of research, it is clear that just increasing density or just building mixed use neighborhoods in a few places is not going to make San Diego a healthier city. We should be working toward “complete communities” with shops within walking distance, sufficient density to support high-frequency transit, safe and inviting sidewalks and street crossings, parks in every neighborhood with plenty of options for physical activity, and a network of bicycle facilities that protect cyclists with more than paint. In some places these are called “20-minute neighborhoods”, because residents can meet their daily needs within a 20-minute walk. We have a few of these neighborhoods, such as Hillcrest, University Heights, North and South Park, Pacific Beach, and Ocean Beach, and they are among the most popular. The same principles can be put into practice throughout the City and the County, though it may take dramatic changes to make separate-use suburbs more walkable. As we make San Diego a healthier and more prosperous place, we need to make sure to consider the needs of residents of each neighborhood, particularly to protect residents of lower-income neighborhoods from being displaced as their areas become more desirable.

Evidence supporting the importance of Circulate San Diego’s work continues to grow. Making San Diego County more walkable, bikeable, and transit-friendly will achieve health, environmental, and economic goals that are supported by most residents. By helping people understand the benefits of complete communities, perhaps we can take the focus off isolated single issues of density and parking. There is encouraging progress in San Diego, and tools such as the mixed use zoning code, climate action plan, and increased funding for walking, bicycling, and transit should make your advocacy more effective. I invite you to investigate the research briefs, infographics, and other resources at