Americans' responses to COVID-19 stay-home orders differed according to population density

In the study, which appeared online September 30 in the journal Landscape and Urban Planning, the researchers examined publicly available Google data based on anonymized mobility information from millions of Android, iPhone, and Google Maps users in the United States to destinations including grocery stores, rail stations, and parks. The researchers analyzed how total movements changed, at the county level, following local shelter-in-place orders. They found relatively large reductions in visits to "essential" destinations such as grocery stores -- but effectively no reduction in "non-essential" visits to parks and other outdoor recreational spots such as parks and beaches.

The analysis, which included all 771 metropolitan counties in Google's dataset from the first day of stay-at-home order in each county until May 11, 2020, showed that in counties classified as densely populated, reductions to essential trips were even more pronounced.

"The main challenge of compliance with stay-at-home orders in dense and compact areas doesn't seem to relate to 'essential' trips to grocery stores, pharmacies, and transit stations -- trips that people in these areas seemed quite willing to reduce," says study senior author Shima Hamidi, PhD, Bloomberg Assistant Professor of American Health in the Department of Environmental Health and Engineering at the Bloomberg School. "This could be due to access to better services such as home-delivery grocery shopping in dense areas. Also, recent evidence shows that residents of dense places are more likely to adhere to the stay-at-home order, being more cognizant of the threat."

Mandatory social distancing and lockdown measures imposed by states and municipalities have been the most widely used public health tools against COVID-19 so far. But the degree to which people comply with these mandates has been unclear and relatively unstudied.

Hamidi and her co-author Ahoura Zandiatashbar, PhD, an assistant professor of Urban and Regional Planning at San Jose State University, found that for all 771 counties covered by the Google dataset, lockdowns appeared to have a sizeable impact on the three major categories of travel they examined. Trips to grocery stores and pharmacies following lockdowns and up to May 11 stayed, on average, 13.3 percent below the local baseline averages established in January and February. Trips to transit stations stayed 37.4 percent below baseline. By contrast, trips to parks, beaches, and other outdoor recreational spots were only 0.4 percent lower on average -- effectively unchanged.

Hamidi suggests that park and beach visits may not have declined because they were allowable under many stay-at-home mandates, may have been important in reducing stress amid the pandemic, and may also have been widely perceived as low risk. However, she also notes that there is some evidence from epidemiological studies suggesting that parks and other outdoor spaces can present a significant chance of virus transmission, especially if relatively crowded.

Hamidi and Zandiatashbar analyzed how trip trends varied according to different factors, and found that trips to grocery stores/pharmacies and transit stations -- often categorized as "essential" trips -- dropped more significantly in denser ("compact") counties, while trips to parks and beaches in these counties slightly increased.

"This is not surprising but could be concerning, since visiting parks during the pandemic has its own risks," says Hamidi. "Parks could be a potential hotspot for the transmission of the virus, especially if people don't physically distance. In addition, the risk of exposure to COVID-19 in parks is potentially even greater among the homeless who use parks frequently, which could eventually elevate the risk of COVID-19 exposure to the general population."

The researchers also analyzed trip changes during lockdown periods and counties' electoral results, and found slightly lower compliance overall, especially related to essential trips, in metropolitan counties where Donald Trump won a higher percent of the vote in the 2016 presidential election.

The researchers observed as well that reductions in the three types of trips tended to deepen in the days just after the announcement of lockdowns, but then lessen as lockdowns wore on.

"We urge decision-makers, planners, and public health officials to design and implement social distancing guidelines specifically for parks and similar areas," Hamidi says, "and to closely monitor people's social distancing behaviors in and travel patterns to parks in relatively dense urban spaces with higher per capita COVID-19 mortality rates."

"Compact development and adherence to stay-at-home order during the COVID-19 pandemic: A longitudinal investigation in the United States" was written by Shima Hamidi and Ahoura Zandiatashbar.

The research was supported by the Bloomberg School's Bloomberg American Health Initiative.