A judge has threatened to jail three union leaders who called a strike of New York city public transport workers.
Get there if you can: New Yorkers found alternative transport
Justice Theodore Jones ordered the union heads to appear before him on Thursday because of the "distinct possibility" they would be jailed.
The union has already been slapped with fines of $1m a day, as New York law bars transport workers from striking.
New Yorkers faced below-freezing temperatures as they made their way to work on the second day of the strike.
With no subway or bus services operating, millions of people once again had to walk, cycle or share cars to get to their workplaces.
Some people woke hours before dawn to beat a ban on cars with fewer than four people entering Manhattan between 5am and 11am.
Janine Colletta, 21, found herself in a traffic jam en route from Queens to lower Manhattan - before 0630.
"I got up three-and-a-half hours early, only so we could sit in traffic with people cursing at us," she told the New York Times.
"I didn't come in yesterday - I couldn't come in. I got a ride today. I don't know about tomorrow."
Manhattan is an island accessible only by bridges and tunnels.
Mayor Michael Bloomberg walked across the Brooklyn Bridge for a second day in a row to get to work.
Later, he said jailing the strike leaders would do no good, and might impede negotiations.
He favours stiffer fines.
"I never thought that putting someone in jail and making them a martyr would help," he said.
The city is not a party to the dispute between the union and the Metropolitan Transport Authority (MTA), which is run by the state of New York.
A lawyer for the union - Transport Workers Union Local 100 - said it could not afford the existing fines, producing tax records showing it had only $3.6m in its accounts.
The Transport Workers' Union's 34,000 members went on strike on Tuesday after talks over their contracts collapsed.
They say they are "tired of being underappreciated" but transport bosses accuse them of "bullying tactics".
The local union's parent organisation does not support the strike.
According to the BBC's Jeremy Cooke, there is a growing mood of frustration with the strike but also a determination to carry on regardless.
Cycle shops reported staying open late as people brought in bicycles that had not been used in years.
"We're getting a lot of flat tyres, mostly on decrepit pieces of garbage that people unearth from their basements at the last possible moment," Todd X of Bicycle Habitat told the Reuters news agency.
First in decades
The TWU and the MTA are in dispute over wage rises, health care and pension costs and the retirement age of employees.
The union argues that cutbacks in benefits are unnecessary as the mass transit system has a $1bn surplus, which the MTA says is for essential reinvestment.
"Transit workers are tired of being underappreciated and disrespected," TWU chief Roger Toussaint said.
MTA says it put a fair offer on the table, and chairman Peter Kalikow called the union action a "slap in the face" for all New Yorkers.
This is the first mass transit walkout in New York since an 11-day strike in 1980, which was calculated to have cost the city billions of dollars.