Officials are considering shutting down the city's transportation system this weekend if conditions from Hurricane Irene become too harsh.
The system can't operate safely with sustained winds of 39 mph or more, MTA chairman Jay Walder said Thursday.
It takes eight hours for the system to shut down and for the MTA to move equipment from low-lying storage areas and secure trains in protected areas, including in the system's underground tunnels, he said.
The MTA said it is working with the city Office of Emergency Management to be ready to evacuate riders from buses, subways, railroads and bridges and tunnels.
The Port Authority of New York and New Jersey said it will have crews on stand-by throughout the PATH train system to deploy extra pumps and sand bags in case of flooding.
The authority is also warning that high winds at bridges and tunnels could mean a temporary ban on tractor-trailers, motorcycles and car-pulled trailers.
Area airports have stockpiles of bottled water, diapers, cots and blankets. Shuttle buses will be available to assist in the movement of stranded passengers.
The city Department of Transportation was also clearing debris from catch basins in 26 flood-prone spots around the city, and moving equipment to higher ground.