Paris metro and other public transport workers were to walk off the job Friday for a huge one-day strike over President Emmanuel Macron's plan to overhaul France's retirement system.
Ten of the city's 16 metro lines will be shut down completely, while service on most others will be severely curtailed, in particular during Friday's rush hours.
Two of the 3 main suburban lines traversing the city will be "very strongly disrupted," the Paris transport operator RATP warned, with just a handful of trains running during only the peak morning and evening hours.
Buses and trams will also be impacted, often with just one in three operating.
Many commuters are expecting a mad scramble for the bike-sharing systems and electric scooters that have mushroomed in the French capital since last year.
US ride-hailing giant Uber is hoping to seize the moment with two free 15-minute rides offered on the Jump electric bikes and scooters it has deployed in Paris.
And the RATP said it was financing 30 free minutes for clients of the Cityscoot network of electric mopeds.
- 'Shot across the bow' -
The three main RATP labour unions have called it "a shot across the bow" against Macron's pledge to implement a "universal" pension system that would do away with dozens of separate schemes for different professions.
It is shaping up to be the biggest metro strike since 2007, when former president Nicolas Sarkozy pushed through a pension reform that moved back the retirement age for most public workers.
During his 2017 presidential campaign, Macron pledged not to touch the current legal retirement age of 62 for most workers.
But Jean-Paul Delevoye, who is leading the reform project, has suggested a points system that would effectively wipe out the more advantageous pensions for a wide range of professions, including those for sailors, notaries and even Paris Opera workers.
More controversially, Delevoye has also proposed making a full pension available only from 64 -- people who retire earlier would have to accept a lower pension: five percent less for someone who stops working at 63, for example.
"We're going to construct a truly universal system where every euro paid in will provide the same rights for everyone, whether a labourer, a shop owner, a researcher, a farmer, a civil servant, a doctor or an entrepreneur," Prime Minister Edouard Philippe said in a speech Thursday.
Consultations are currently being held with labour unions, and the government wants parliament to vote on the project next spring.
But the government is likely to face further opposition in coming weeks, with lawyers, airline pilots and stewards, and medical workers calling a strike for Monday.