The roar of the engines, the passing landscapes, and suddenly… a blinding flash. The fear of speeding grips every driver at the sight of a speed camera, and you may have already experienced it. However, French motorists benefit from a certain flexibility thanks to the margins of error applied by the road authorities on the different types of radars. These tolerances are compensation for technical imperfections of the measuring devices.
At what maximum speed should you drive?
Margins of error are always to the driver's advantage and vary depending on the type of radar and the speed recorded. For fixed speed cameras, omnipresent on our roads, the margin is set at 5 km/h for speeds not exceeding 100 km/h. Beyond that, it increases to 5% of the measured speed. Concretely, on a road limited to 90 km/h, a driver flashed at 96 km/h will see his speed reduced to 91 km/h on the report.
The margin for fixed radars
| Vitesse max. | Marge | Speeding from: |
|---|---|---|
| 80 km/h | 5 km/h | 86 km/h (speed retained: 81 km/h) |
| 90 km/h | 5 km/h | 96 km/h (speed retained: 91 km/h) |
| 110 km/h | 5% | 116 km/h (retained speed: 111 km/h) |
| 130 km/h | 5% | 137 km/h (retained speed: 131 km/h) |
Mobile radars (whether embedded in law enforcement vehicles or operated by private providers) benefit from a more generous margin because they are even less precise. It rises at 10 km/h to 100 km/h, then to 10% for higher speeds. This difference is explained by the increased complexity of moving measurements. Thus, on a motorway limited to 130 km/h, a motorist flashed at 144 km/h by a mobile radar will only be held at 131 km/h, narrowly escaping the fine.
144km/h corrected to 131km/h
These margins are not a coincidence and Road Safety is transparent about the methodology: they result from in-depth reflection on the technical limits of the devices and the need for fairness in the application of the law. They make it possible to take into account possible inaccuracies in radars and vehicle speedometers, which thus avoids abusive disputes and unjustified sanctions.
-The margin for mobile radars
| Vitesse max. | Marge | Speeding from: |
|---|---|---|
| 80 km/h | 10 km/h | 91 km/h (speed retained: 81 km/h) |
| 90 km/h | 10 km/h | 101 km/h (retained speed: 91 km/h) |
| 110 km/h | 10% | 122 km/h (retained speed: 111 km/h) |
| 130 km/h | 10% | 144 km/h (retained speed: 131 km/h) |
Be careful, these margins should not be seen as an invitation to systematically flirt with the limits: they remain a technical tolerance, not an acquired right. As you probably know, respecting speed limits is the best guarantee of safety on the roads. With the proliferation of radars on French territory, it is better not to play with fire.
For drivers who want to stay on track and not pay fines for their driving, these margins provide peace of mind. A slight involuntary overrun will not automatically result in a fine, but caution is still required. These margins of error for 2025 are a subtle balance between rigor and pragmatism in road safety policy.
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