The cameras, known as 'average speed cameras' or 'radars-tronçon' in French, use several positions to measure a car's average speed.
The first of the new cameras has been installed in the eastern Doubs region.
According to national road safety agency Sécurité Routière, the cameras are designed to stop the dangerous practice of drivers who slow down suddenly for normal cameras before speeding up again.
The cameras will not flash but warning signs will be placed before the controlled area. Drivers will see speed panels that tell them how fast they are travelling.
Sécurité Routière said the cameras would be placed on roads that are "particularly accident-prone". These include roads that narrow suddenly, have many bends or close to tunnels and bridges.
Road safety organisations welcomed the new cameras.
"These cameras are a response to those drivers who play with fixed cameras, braking suddenly and then speeding up again," said Chantal Perrichon of the League against road violence.
Some motoring organisations were concerned the cameras could be used excessively.
"They are useful in dangerous spots and to replace the large number of cameras that are annoying," said Louis Derboulle from the 40 million drivers organisation.
He told Liberation newspaper that "if they are used on a 30 to 40 kilometre stretch of the motorway, that's a scandal. That's just designed to make money."