Exploring the impact of social distancing on emergency call volume using Google’s mobility dataset
The COVID-19 pandemic has altered our lifestyles in an unprecedented way. In the last two months, there has been a dramatic reduction in the number of people commuting to work, dining at restaurants, and shopping at retail stores. These changes in movement patterns can greatly affect the emergency call volumes of fire departments. If the social distancing measures are effective, one can expect that emergency incidents related to COVID-19 symptoms will eventually decrease over time. However, the reduced mobility can also affect the frequency of other incident types such as traffic accidents and injuries. In this blog post, we will examine the impact of social distancing on emergency call volume for two departments that utilize the National Fire Operations Reporting System (NFORS) data system. The two departments include Miami-Dade Fire Rescue Department in Florida (*which does not include the City of Miami) and the Columbus Division of Fire in Ohio.
How can we quantify how much social distancing a community is doing?
In order to help researchers and public health officials understand the impact of social distancing in their communities, Google has released Community Mobility Reports. These reports provide aggregated and anonymized data collected from mobile phones whose users have opted into the Location History setting. At the county level, the dataset provides the percent change in visits to various types of places relative to a baseline. The baseline is calculated from the daily number of visits observed before the U.S. implemented widespread measures in response to the pandemic. In this blog post, we explore four location types from the mobility dataset:
Grocery & pharmacy- Mobility trends for places like grocery markets, food warehouses, farmers markets, specialty food shops, drug stores, and pharmacies.
Retail & recreation- Mobility trends for places like restaurants, cafes, shopping centers, theme parks, museums, libraries, and movie theaters.
Residential- Mobility trends for places of residence.
Workplaces- Mobility trends for places of work.
How is social distancing affecting total call volumes?
First we examine the impact of mobility changes on total call volumes. The total call volume is based on the daily count of all incidents reported in NFORS. For simplicity, we show the call volume as a percentage change relative to baseline. The baseline was computed as the average number of calls per day from January 1st to February 6th. To make it easier to visualize the trends, we apply a moving average filter with a window of seven days to both the daily call volume data and the mobility data. This filter removes the noise caused by day-to-day fluctuations in these quantities. For example, any point shown on a day is actually the average value of that day, plus the three days before it, and the three days after it. This approach also removes the impact of the day-of-the-week because every point is an average of all seven days of the week. The resulting plot is shown below for Miami-Dade Fire Rescue Department, along with the changes in mobility for Miami-Dade County.
The same plot is generated for the Columbus Division of Fire using mobility data from Franklin County, shown below:
Both of these plots reveal similar trends. Here are some key takeaways:
- There has been a noticeable downward trend in total call volume resulting in 20% fewer calls than before social distancing measures were implemented.
- Both communities began reducing visits to retail/recreation locations and workplaces around March 10th, which is about two weeks before shelter-in-place orders were implemented.
- There was a spike in visits to grocery/pharmacy locations from March 8th to March 17th. After that time, these visits have been about 20–30% lower than the baseline.
Which types of call volume are most affected by social distancing?
After seeing that total call volumes have declined, we were curious about which types of calls were driving these trends. We examined many different incident types for each department, and found that the most notable changes were in calls potentially related to COVID-19 symptoms, traffic accidents, and injuries. Because incident types are reported differently for each department, we used two slightly different approaches to identify these particular incidents.
Here are the filters we used to identify the incident categories for Miami-Dade Fire Rescue Department:
Traffic calls- Any incident with the string “traff” in its type on the Computer Aided Dispatch (CAD) system. This string captures incident types that have either “traffic” or the abbreviation “traff.”
Injury calls- Any incident with the string “injur” in its type. This string captures incidents that have either “injury” or “injuries” in their types. This string appears to exclude traffic related incidents.
Fire calls- Any incident with the string “fire” in its type.
Calls with COVID-19 keywords- Although Miami has a “FEVER WITH TRAVEL” incident type that was introduced in light of the recent pandemic, we were interested in all calls that could be related to COVID-19 symptoms, even if the patient did not recently travel. As a result, we identified incidents that have at least one of the following strings in the comments: “corona virus”, “coronavirus”, “cough”, “fever”, “covid.”
The resulting plot is shown below. Because there is not a meaningful baseline for “Calls with COVID-19”, we instead show the daily number of calls rather than a percent difference relative to a baseline. In order to show the mobility trends, we show the percent change relative to the baseline for visits to workplaces with the left axis. All other curves are plotted with the right axis.
For the Columbus Division of Fire, we used slightly different filters due to differences in reporting:
Traffic calls- Any incident with the type “VEHICLE ACCIDENT.”
Injury calls- Any incident with the string “injur” in its type. This string captures incidents that have either “injury” or “injuries” in their types.
Fire calls- Any incident with the string “fire” in its type.
CE calls- Any incident with the type “CONTAGIOUS EMERGENCY.” This is a new incident type that was introduced in the wake of the COVID-19 pandemic. This is why there are no calls of this type before March 12th. For more information, we recommend reading this blog post.
The resulting plot is shown below. The apparent uptick in fire calls that occurs between March 17th and March 24th is because of the unusually large call volume on March 20th due to storms.
Looking the trends in the incident types for these two fire departments, here are some takeaways:
- Visits to workplaces have been near 50% of the baseline for both communities since the end of March. The most recent data for April shows a downward trend in the number of incidents with COVID-19 related keywords (for Miami-Dade) and incidents with the “CONTAGIOUS EMERGENCY” type (for Columbus). This trend may be evidence that the social distancing measures are working.
- The reduced mobility appears to be linked to fewer injuries and traffic incidents. This trend is likely because people are driving less and avoiding other risky activities. These trends are more significant for Miami-Dade than for Columbus (Franklin County), however.
- Fire call volume does not appear to have changed significantly for either department.
Conclusions
In this blog post, we use data from NFORS and Google’s Community Mobility Report to examine the impact of social distancing on emergency call volumes. Although there is a general downward trend in total call volumes, an investigation of the individual incident types reveals a deeper story. We see that calls potentially related to COVID-19 increase sharply in mid-March, but the most recent data show that the frequency of these incidents is beginning to decrease. The reduced mobility also appears to be linked to a reduction in the frequency of incidents related to traffic accidents and injuries. The call volume for fire related incidents appears relatively unchanged. Going forward, these data can help departments monitor the impact of easing restrictions on their call volumes.
If your organization participates in NFORS and you would like to see a similar analysis for your department contact us today at hello@i-psdi.org . If your department does not yet participate in NFORS, schedule a demo to see the power of analytics https://www.eventbrite.com/e/nfors-demo-registration-45782334194 .
