Ridership across the MTA’s commuter rails, subways and buses dropped dramatically as New Yorkers avoid close-quartered of buses and trains in a bid to halt the spread of coronavirus, Gov. Andrew Cuomo’s office revealed Thursday.

Total subway ridership Wednesday was down a whopping 18.5 percent from the same Wednesday last year, MTA spokeswoman Kayla Shults said, while bus ridership was down 15 percent.

The city’s commuter rails, which carry fewer people on a normal day, saw even steeper dips Thursday morning — 48 percent for Metro-North and 31 percent for the Long Island Rail Road versus the second Thursday of last March.

Bridge and tunnel automobile crossings also dropped 6.7 percent on Wednesday compared to the previous year, the MTA said. Those tolls are a key source of revenue for the authority, providing $2.2 billion last year.

Buses and subways chief Sarah Feinberg said in a radio interview Thursday that she expects ridership to continue to drop, and that the agency is preparing multiple contingency plans, including reduced service.

“If the CDC or the Department of Health at some point tells us to completely change how we operate the system, we will do that,” she said. “For now, a lot of people are using the system, and we will continue to execute on that.”

The $18 billion-per-year transit agency relies on farebox revenue to keep the system open — meaning the ridership drop could ultimately require service cuts, Feinberg conceded.

“If ridership goes down significantly, that gives us farebox issues,” Feinberg said. “I’m not sure we’re in a different position than any other agency of our type in the country.”