Commuting by car, regardless of whether the vehicle is electric or gas-powered, continues to pose health risks due to sedentary behavior, according to Lawrence Frank, a professor of urban studies and planning at UC San Diego. In a new commentary published in the American Journal of Preventive Medicine, Frank revisits findings from his 2004 study that linked increased time spent in cars with higher obesity rates.
Frank’s original research was among the first to connect neighborhood design and public health. The study found that each additional hour spent in a car raised the odds of obesity by 6%, while walking an extra kilometer reduced those odds by 5%. This work helped popularize concepts like walkability and influenced tools such as Walk Score.
“You can spend just as much time sitting in an electric vehicle as you can in a gas one,” said Frank. “Every hour in a car will still be a 6% increase in the likelihood of obesity.”
The commentary, co-authored with Jacob Carson from the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science-San Diego State University Joint Doctoral Program in Public Health, reviews two decades of evidence showing how built-environment design affects not only obesity but also heart disease, diabetes, and mental health.
Frank notes that while technological advances like electric vehicles have improved air quality, they do not address sedentary lifestyles caused by city layouts focused on cars rather than walking or cycling. He emphasizes that transportation budgets often overlook these health costs.
“We are still driving blind,” Frank said. “We’re acting like these things don’t exist, but they’re so huge.”
Carson added: “The last 20 years of technological progress haven’t changed the original findings of this paper, and neither will the electrification or autonomization of cars. Robust public transportation and safe cycling and walking infrastructure are still relevant solutions to the challenge of creating healthy and sustainable communities.”
Frank’s team is developing assessment tools for cities to quantify health impacts when considering investments in streets, sidewalks, or transit using cost-benefit frameworks similar to those used for congestion or emissions.
“Most people do not find the time to be physically active to counter the adverse effects of sedentary driving time,” Frank said. “You have to reduce car dependence — and integrate active transportation into daily life.”
A related study led by Frank highlights how small-scale improvements—such as adding sidewalks, benches, shade trees, and safer crossings—can encourage more physical activity among residents. These features are particularly beneficial for older adults and can offer significant returns on investment for public health.
“Investing in those small features is fairly easy to do; it’s fairly inexpensive. That’s going to give you the biggest return on investment of anything you can do to improve public health through transportation investment,” he said.
He also points out that low-income neighborhoods stand to benefit most from these changes: “Focus the investment on active transportation and pedestrian features…in the places where people are most likely to develop chronic disease.”
Frank concludes: “We’ve learned exactly how the built environment shapes behavior. Now it’s time to put that knowledge to work — because every mile we walk instead of driving matters.”
