(CNN) For the first time in its 115-year history, New York City deliberately shut down its entire subway system Wednesday morning.
The reason: The Metropolitan Transportation Authority (MTA) deep-cleaned to prevent spread of the coronavirus.
"Extraordinary times call for extraordinary measures," MTA Chairman Patrick Foye said late Tuesday.
The New York City subway has been shut down because of weather: Hurricane Irene in 2011 and Hurricane Sandy in 2012. During the blizzard of 2015, the system canceled passenger service, but equipment trains kept running.
But this is the first planned shutdown.
The cleanings will be done on a nightly basis, from 1 a.m. to 5 a.m. When the cleaning is done, every single subway car will be disinfected.
"This is critical to ensure the health and safety of our employees and customers," said Foye.
To accommodate the loss of train service, the MTA is adding several hundred buses to its typical overnight routes to make sure essential workers have access to transportation.
Subway officials warned New York residents that there may be hiccups in executing the unprecedented closure.
"If this were a normal moment, we would have planned this for months," New York City Transit President Sarah Feinberg said.
Subway ridership during the coronavirus crisis is down 90% from pre-pandemic times. But about 11,000 people still have used the subway from 1 a.m. to 5 a.m. daily during the pandemic, the MTA said.
The pandemic already had forced changes to service. MTA has installed vinyl shields on buses to further separate passengers and drivers, and it is checking more than 3,500 employees a day for fevers.
More than 80 MTA employees, including at least 50 who worked in the subway, have died from complications related to coronavirus, the authority says.