New York City's 6,300 subway cars and 4,600 buses were still Tuesday morning as Local 100 of the Transport Workers Union went out on strike.
Although the strike is illegal under state law, the union decided to pull its 37,000 members from service over the issue of pension and health benefits for future employees.
Some 7 million people ride the on the system every weekday.
The union's executive board voted 28 to 10, with five members abstaining, to start the strike.
At 3:25 a.m., Peter Kalikow, the chairman of the Metropolitan Transportation Authority said the authority and the state attorney general would go to state court to seek a contempt citation against the union.
City officials have prepared an emergency plan that would increase ferry service, allow taxis to pick up multiple fares, close several streets to traffic except for buses and emergency vehicles, and prohibit cars with fewer than four passengers from entering Manhattan during the morning rush, UPI reports.