The cameras, perched on four-metre tall posts, have been tested in Marseille and Strasbourg and now 400 of them will be rolled out over the coming year, with three times that number to be set up next year, France Info reported.

The devices are capable of not only clocking your speed but also recording a variety of other misdemeanours, such as phoning while driving, sudden swerving, not wearing a seatbelt, or overtaking on the right, which is illegal in France.

But in the short term the cameras, whose brand name is the Mesta Fusion 2 and which can monitor eight lanes of traffic and several vehicles at once, will be used only to catch people speeding.

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There will be four decoy cameras for each operating one, and the decoys and the real ones will be switched regularly to prevent drivers figuring out which are the ones catching them breaking the law.

The new cameras are said to be far harder to vandalise than existing ones.

The French government last week blamed a steep rise in road deaths in February on the yellow vest movement, during which three quarters of speed cameras on the country’s roads have been vandalised or put out of action in recent months.

Official figures said that 253 people were killed on the roads in France in February, a 17.1 percent increase on the same time last year.

Previously road deaths had been going down. There were 3,259 deaths on the country's roads in 2018 – down from 3,448 deaths the previous year.

But they have started to rise again since the yellow vest movement began late last year.

Some protesters angry about planned rises in fuel tax and the rising costs of travel to work, and about a recent lowering of speed limits on some roads, turned their ire on speed cameras.