DEKRA: Do not rely blindly on the automatic headlights in fog

"The automatic light control has brought a lot of safety gains. Nevertheless, one should not blindly rely on the technology," says Denis Preissner, accident researcher at DEKRA. "The light sensors in many vehicles only distinguish between light and dark and mostly only switch on the daytime running lights in fog, drizzle, or spray, but not the low beam. In the latest vehicles, the sensors are becoming increasingly sensitive, yet it is important to remain attentive and pay attention to the light settings."

Daytime Running Lights Not Sufficient in Poor Visibility

In daytime running light mode, the front headlights shine dimmer, and the rear lights remain completely off. This makes the vehicle much harder to recognize from the front and back, leading to an increased risk of critical situations.

The road traffic regulations require that even during the day, low-beam headlights must be turned on if visibility is significantly impaired by fog, snowfall, or rain (§ 17 Abs. 3 StVO). In such situations with diffuse light, drivers must take the initiative to switch on the low-beam headlights themselves.

"The earlier, the better," says Preissner.

Fog Lights: Better Illumination for Close Range

Visibility generally improves in diffuse light when the fog lights are turned on. These spread the light more broadly than the regular low beams and illuminate the road better in the close range. Without low beams, self-dazzle is also reduced. Switching to fog lights is allowed when visibility is severely impaired, but it is not mandatory.

"For driving in fog during the dark, we recommend turning on fog lights, if available, in addition to the low beams to achieve optimal visibility and road illumination," said Preissner. "High beams, on the other hand, are not very useful in fog or snow. They are strongly reflected by the fog droplets and thus worsen visibility due to self-dazzle."