Since August 9, travelers who use the train for so-called "long distance" journeys are required to have a health pass.
On the occasion of the crossover on August 15, station controls should be numerous, and some railway workers fear having trouble with anti-pass.
The truth test for the health pass in public transport.
A large crowd is expected in stations and trains from Friday evening until Sunday.
The SNCF expects some 930,000 travelers over these three days of crossover.
The sanitary pass controls on the platforms and in the trains started last Monday and are starting to be well established.
But what about the big day crowds?
The railway workers are both confident and vigilant.
"It will be a full-scale exercise, on a large scale, with a much greater flow of travelers. We are rather confident since customers are willing to lend themselves to the exercise", explains to Europe 1 Frédéric Fournier, number three of the Unsa Railway.
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A risk of conflict with the employees in charge of controls
While a new day of mobilization against the health pass is scheduled for Saturday August 14 in several cities, this unionist however fears to see the stations transformed into places of demand.
"There is a protest movement against this health pass and we are extremely vigilant that the people who participate in this movement do not use the control system as a platform, by coming into conflict with SNCF employees", Frédéric Fournier points.