You may only fit your vehicle with snow chains if the road is snowed under, regardless of the time of the year. It may sound like a statement of the obvious, but remember that it means you must remove the chains once you reach a road whose surface has been cleared. The reason is that snow chains damage the asphalt.
A round blue sign showing a tire with chains usually indicates areas where snow chains are necessary, and a similar sign with a red line across it signals the end of that obligation. But these signs (known respectively as B26 and B44 in the French law governing road signs) are becoming less frequent, as snow conditions vary each year, and replaced with temporary notices on road signs.
The chains must be attached to at least two drive wheels, which may be the front or back wheels depending on the make of your car. This ensures that the extra grip on the snow is used to propel your car.
When your car is fitted with snow chains, you may not drive any faster than 50 kph (31 mph)--not that you could go much faster on snow, anyway.
While you may use snow chains at any time of the year if the climatic conditions make them necessary, studded tires are a different matter. The laws governing road usage (Code de la Route in French) authorize their use only from the Saturday before November 11 until the last Sunday of March of the following year, unless local authorities decide otherwise.
The fines for misuse of snow chains may be as high as 750 euros ($960).
