Fog sharply reduces visibility and requires slower driving, a greater following distance and the proper use of lights. The vehicle must be visible both to those driving ahead and to those behind. That is why low-beam headlights should be used, as they also turn on the rear lights, rather than relying solely on the vehicle’s daytime running lights. If available, fog lights can also be switched on.
„Never use high beams,“ the US National Weather Service advises. The reason is that the light reflects off the droplets in the air and creates glare, further making it difficult to see the road.
The distance from the vehicle ahead should be increased to allow time to react in the event of sudden braking or a change in traffic. In fog, drivers should keep an eye on the road markings to remain in the correct lane.
In 2020, Bulgarian legislation added sign A42 "Reduced Visibility", which also warns of fog. If you see it but visibility on the road is good, stay alert and reduce your speed.
In extremely dense fog, when visibility is nearly zero, the recommendation is to first switch on the hazard lights and then take the vehicle out of the traffic flow. The safest place is a parking lot or another pull-off away from the roadway.
If there is no parking lot or entrance to a safe place nearby, the vehicle should be pulled as far to the right as possible. After stopping, all lights except the hazard lights should be switched off, the handbrake should be applied and the driver’s foot should be taken off the brake pedal. This prevents the brake lights from remaining on and keeps the vehicle from appearing to be moving to other drivers.