 We're using predictive analytics. Fire Chief Tiffany Green says they know when crews are busier. We're putting peak units in certain areas. We're putting a peak unit in Greenbelt, for example, because we know during a certain time call, there's going to be more EMS calls, and we want to have an EMS unit available to run those calls. John Dome in WTOP News. And Prince George's County officials say they're currently operating with 251 career firefighters short of a full staff.