Starting on May 6, 2020, as a result of the COVID-19 pandemic in New York City, stations were closed between 1:00 a.m. and 5:00 a.m. for cleaning and disinfecting; the overnight closures will be a temporary measure that will end once the pandemic is over. Over 500 trains continue to run between 1 a.m. and 5 a.m. every 20 minutes, carrying only transit workers and emergency personnel. The trains keep running because there is not enough space in the system to store all trains simultaneously, and so that they can easily resume service upon the start of rush hour at 5 a.m. In February 2021, the overnight closures were shortened to between 2 and 4 a.m.