Clause 19.3

In case of reduced visibility in the direction of travel caused by the headlights of oncoming vehicles, the driver must reduce the speed to a level that does not exceed the safe speed according to the actual visibility conditions of the road in the direction of travel, and in case of being dazzled—stop without changing the lane and turn on the hazard warning lights. Resuming movement is allowed only after the negative effects of dazzling have passed.

This clause directly establishes the driver's obligation in case of reduced visibility due to the headlights of oncoming vehicles—to reduce speed to a safe level (and a complete stop is provided specifically in case of dazzling).

Clause 1.10 (term "Visibility in the direction of travel")

Visibility in the direction of travel is the maximum distance at which, from the driver's seat, the boundaries of road elements and the positions of road users can be clearly recognized, allowing the driver to orient themselves while driving, in particular to choose a safe speed and perform safe maneuvers.

This definition explains that reduced visibility directly affects the ability to choose a safe speed.

Clause 1.10 (term "Safe speed")

Safe speed is the speed at which the driver is able to safely control the vehicle and maintain control of its movement in specific road conditions.

This term clarifies that "safe speed" is determined by actual conditions (including real visibility), and it is to this speed that one must reduce according to the requirement of clause 19.3.

Thus, the correct answer is "Reduce speed to a safe level," considering that according to the definition of the Traffic Rules, safe speed is the speed that ensures control of the vehicle in specific conditions, and clause 19.3 directly requires reducing speed to a safe level in case of reduced visibility due to the headlights of oncoming vehicles.

While driving at night or in twilight, the headlights of oncoming vehicles can reduce visibility in your direction of travel. Visibility in the direction of travel is the distance at which the driver from their seat can clearly recognize the road and road users in order to choose the correct speed and timely perform necessary actions.

When, due to the headlights of oncoming traffic, you start to see the edges of your lane, the roadside, pedestrians, or obstacles less clearly, you can no longer guarantee that your stopping distance will be less than the distance you can actually see. That is why clause 19.3 of the Traffic Rules requires you in such a situation to reduce your speed to one that is safe for the actual visibility. Safe speed is the speed at which you maintain full control of the vehicle under the existing conditions.

In practice, this means: as soon as the light from oncoming headlights makes it harder for you to assess the road situation ahead, you should smoothly reduce your speed (for example, by taking your foot off the accelerator and, if necessary, gently braking) so that you can react in time to any danger within the distance you can actually see. Stopping with hazard lights on is only required when you are actually blinded; the question refers to reduced visibility, so reducing speed is sufficient.

Therefore, the correct answer is "Reduce speed to a safe level," because when visibility is reduced by the headlights of oncoming vehicles, the Traffic Rules require you to lower your speed to a level that matches actual visibility and ensures control and the ability to stop within the visible distance.