New York's subways and buses are back in action Friday, after a three-day transit strike threw America's largest city into turmoil.

New York's Transport Workers Union voted Thursday to send its 33,000 members back to work without a contract. The walkout ended after union leaders were threatened with jail for defying a state law against strikes by public workers.

Contract negotiations are expected to continue, as the city and the union haggle over pension and health benefits.

The strike inconvenienced millions of commuters and cost the city an estimated $1 billion. The union was being fined $1 million for each day of the walkout, the first of its kind in 25 years.