“In our analysis focusing on Los Angeles County, unexpected traffic delays beyond the usual congestion led to a 1% increase in fast food visits. That might not sound like a lot, but it’s equivalent to 1.2 million more fast food visits per year in LA County alone. We describe our results as being modest but meaningful in terms of potential for changing unhealthy food choices,” said study author Becca Taylor, assistant professor in the Department of Agricultural and Consumer Economics, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois.

Taylor and her co-authors had access to daily highway traffic patterns over more than two years in Los Angeles, along with data showing how many cell phone users entered fast-food restaurants in the same time period. With these data, the team created a computational model showing a causal link between unexpected traffic slow-downs and fast food visits.

This pattern held at various time scales, including 24-hour cycles and by the hour throughout a given day. When analyzed by the day, traffic delays of just 30 seconds per mile were enough to spike fast-food visits by 1%.

“It might not be intuitive to imagine what a 30-second delay per mile feels like,” Taylor said. “I think of it as the difference between 10 a.m. traffic and 5 p.m. traffic.”

When the researchers broke the day into hour-long segments, they found a significantly greater number of fast food visits when traffic delays hit during the evening rush hour. At the same time, grocery store visits declined slightly.

“If there's traffic between 5 and 7 p.m., which happens to be right around the evening meal time, we see an increase in fast food visits,” Taylor said. “Drivers have to make a decision about whether to go home and cook something, stop at the grocery store first, or just get fast food.”

Considering every major city has both traffic and fast food restaurants lining highway feeder roads, it’s not a stretch to extrapolate the pattern beyond Los Angeles. Taylor and her co-authors say the link between traffic and unhealthy food choices is just one more reason policymakers around the country and the globe should prioritize infrastructure reforms to ease congestion.

“Our results contribute to the literature suggesting time constraints are really important to the food choices people make. Any policies aimed at loosening time constraints — and traffic is essentially lost time — could help battle unhealthy eating,” Taylor said. “That could mean improvements in infrastructure to mitigate traffic congestion, expanding public transport availability, and potentially increasing work from home opportunities.”

The study, “Slow traffic, fast food: The effects of time lost on food store choice,” is published in the Journal of Urban Economics [DOI: 10.1016/j.jue.2025.103737]. Authors include Panka Bencsik of Vanderbilt University, Lester Lusher of the University of Pittsburgh and IZA, and Becca Taylor.