In France, most serious accidents occur when weather conditions change: rain, fog, snow, or black ice. The good news is that the Highway Code provides simple, quantified rules. Once you know them, driving in bad weather becomes a matter of organized common sense. Here is the essential information, designed for those discovering French roads.
Rain reduces your maximum speeds
As soon as it rains, the maximum authorized speeds automatically decrease. You do not need a sign: the rule applies everywhere, to all drivers (even experienced ones).
- Motorway: 130 → 110 km/h
- Dual carriageway (separated lanes): 110 → 100 km/h
- Road: 90 → 80 km/h
Beware of a frequent subtlety: on a two-way road without a central divider already limited to 80 km/h, the speed remains 80 km/h in the rain. There is no further reduction. Only roads with a 90 km/h limit drop to 80.
And when visibility really drops? If you can see less than 50 meters, the maximum speed is 50 km/h everywhere, including motorways. To estimate these 50 meters on a motorway, a practical reference point: the white markers along the side of the road are spaced 50 m apart. If you can barely distinguish the next marker, you are at the limit: ease off the accelerator.
Safe following distance: the 2-second rule
The distance separating you from the vehicle ahead must give you enough time to react. The most reliable method is the 2-second rule.
Spot a fixed point (a sign, a bridge, a road marking line). When the vehicle ahead passes it, count "one thousand one, one thousand two." If you reach the point before finishing the count, you are too close.
- In rain or snow, double it: aim for 4 seconds.
- At 130 km/h, these 2 seconds represent approximately 72 meters, equivalent to two road marking lines spaced on a motorway (each white line plus its gap measures 39 m).
Failing to respect safe distances is costly: a €135 fine and loss of 3 points. Beyond the cost, it is one of the primary causes of pile-ups.
Aquaplaning and tire condition
When a film of water gets between the tire and the road, the wheels lose contact: this is aquaplaning. The car floats and no longer responds to steering. The correct reaction: do not brake abruptly, do not steer sharply, gently lift your foot off the accelerator, and keep the steering wheel straight until the tires regain grip.
Prevention relies on tires. The tread depth must be at least 1.6 mm (this is the legal minimum). Below this, water cannot evacuate, and the risk skyrockets. Also check pressure regularly.
Black ice, snow, and the Mountain Law
Black ice is treacherous, especially in the morning and on bridges, which freeze first. "Black ice" is a thin layer of transparent ice, almost invisible on asphalt: the road simply looks wet. At the slightest doubt in cold weather, slow down and avoid any sudden movements.
Under the Mountain Law, in municipalities designated by prefectures, winter equipment is mandatory from November 1st to March 31st. Specifically, you must have either 3PMSF winter tires (the snowflake inside a three-peaked mountain symbol) or chains or snow socks on board. Important: since November 1, 2024, tires marked only M+S are no longer accepted; the 3PMSF marking is now required.
Using your lights correctly
Lights are your best ally in poor visibility, provided you follow the rules.
- Front fog lights: authorized in fog, snow, or heavy rain. They complement or replace dipped headlights. Turn them off as soon as visibility improves.
- Rear fog lights: they do not illuminate; they signal. They are authorized only in fog or falling snow, and prohibited in simple rain (being very powerful, they dazzle the driver behind you). You can turn them on in these conditions, but it is never mandatory: it is up to the driver to judge. Leaving them on incorrectly is a 4th-class offense: fixed fine of €135 (€90 reduced).
- At night: use main beams on deserted roads, but switch back to dipped headlights as soon as an oncoming vehicle appears or you are following someone, to avoid dazzling them.
- Tunnels: turn on dipped headlights before entering and maintain safe distances; locate emergency exits.
In the mountains
On narrow mountain roads, priority goes to the vehicle going uphill: it is the downhill vehicle that must pull over or reverse if necessary. When descending, do not overuse the brake pedal, which overheats and loses efficiency: use engine braking by downshifting.
Key takeaways
- Rain: Motorway 130 → 110, dual carriageway 110 → 100, road 90 → 80. A road already at 80 km/h stays at 80 (no reduction).
- Visibility < 50 m: 50 km/h everywhere. Distance: 2 seconds in good weather, 4 seconds in rain.
- Distances not respected: €135 and 3 points deducted.
- Rear fog light: authorized (never mandatory) in fog or snow, prohibited in rain. Incorrect use = €135 (4th class).
- Mountain Law (Nov 1–Mar 31): 3PMSF tires or chains mandatory; M+S alone is no longer sufficient since November 1, 2024.
- Mountains: priority to the vehicle going uphill, engine braking when descending.