By sunset a judge had fined the transport union $1m (£570,000) a day for each day the action continued, and New York's mayor, Michael Bloomberg, had branded it "thuggish", "selfish" and "shameful". The union was in contempt of the Taylor Law, which bans strikes by public employees and carries penalties of two days' pay for each day.

The union has yet to respond to the ruling. But yesterday New York had already been transformed. In a city where commuters avoid eye contact before their first cup of coffee, people were welcomed into the vehicles of strangers as the police rigorously enforced a four-per-car minimum below 96th street in Manhattan.

Cradling a cup of hot coffee in the hope that it would keep his hands warm on the long walk over Brooklyn Bridge, right, Jim Topokowski said: "My normal commute is 20 minutes. This will take me at least an hour. I only found out it was on when I woke up so I'm way behind and seriously pissed [off]."

The strike is focused on pay and pension entitlement. The Metropolitan Transport Authority is offering 3% this year with higher rises over the next two years. Also, future workers' pension contributions will treble from 2% to 6% of wages over the first 10 years of employment.

The union, pointing to a $1bn surplus the MTA has accrued this year, opposes the extra pension contributions and would settle for an 8% wage rise. The last transport strike in the city was in 1980. That lasted 11 days, but it took place in the spring.

The union president, Roger Toussaint, said the union board voted overwhelmingly to strike. "This is a fight over dignity and respect on the job, a concept that is very alien to the MTA. Transit workers are tired of being underappreciated and disrespected."

But Mr Bloomberg said: "This is not only an affront to the concept of public service, it is a cowardly attempt by Roger Toussaint and the TWU to bring the city to its knees to create leverage for their own bargaining position."

Coming in one of the busiest shopping weeks of the year, in a city where 7 million people commute to work, the strike could cost New York up to $400m a day, says Mr Bloomberg.

Back near Brooklyn Bridge, drivers hovered in search of more passengers so they would be allowed into Manhattan, while fleets of bicycles edged into their own two-wheeled traffic jam.

"It's very inconvenient," said Jason Warwin, 32, who zig-zagged through Brooklyn to pick up four work colleagues before heading up to Harlem. "But I completely support the transit workers. What this strike shows is that the city really needs them and should pay them accordingly."