Millions of motorists are expected to hit France's roads this weekend as the traditional changeover between July and August holidaymakers gets underway, with traffic forecaster Bison Futé warning of severe congestion across much of the country.

The busiest period will run from Friday, July 31st to Monday, August 3rd, with heavy traffic expected on routes to the Atlantic coast, the Mediterranean and the Alps.

Saturday, August 1st has been classified 'black' for departures nationwide, the highest warning level issued by traffic watchdog Bison Futé, meaning conditions are expected to be "extremely difficult". The agency advises drivers to postpone their journey if possible. Red means the traffic is 'very difficult', orange 'difficult' and green 'normal'.

The 'chassé croisé' weekend refers to the annual holiday crossover when people leaving for vacation and those returning travel at the same time, creating major traffic jams. This usually occurs when those taking their vacation in July switch with those leaving in August.

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