35.47. The distance to an oncoming vehicle in fog always appears greater, and its speed appears lower than it actually is:
UAДистанція до зустрічного автомобіля в тумані завжди здається більшою, а швидкість меншою, ніж насправді:
This exam question from the Traffic Rules of Ukraine concerns road safety in difficult weather conditions and checks whether the driver understands how fog affects visual perception and the risk of collision. In conditions of poor visibility, errors in judging distance and speed are especially dangerous, because decisions (braking, refusing a maneuver, choosing a gap) need to be made faster, and there is actually less reaction time than it seems.
In essence, this tests knowledge of the sections of the traffic rules regarding poor visibility and the choice of safe speed and distance: terms from clause 1.10, the duty to be attentive (clause 2.3), requirements for safe speed in conditions of poor visibility (clauses 12.1–12.2), maintaining distance (clause 13.1), and the use of lighting devices, in particular fog lights (clauses 19.1 and 19.4). In the theoretical exam, it is important to understand that fog scatters headlight beams and "eats up" contrast and visual cues, so an oncoming vehicle is often perceived as being farther away, and its approach speed seems lower than it actually is.
The correct answer is the one that confirms this optical illusion: in fog, a driver tends to underestimate the danger of closing distance, because they mostly see blurred lights and an incomplete picture of the road. The incorrect answer denies the typical fog-related error in assessment, due to which drivers leave themselves too little time for braking and may mistakenly start a maneuver or fail to reduce speed.
The practical conclusion for the driver is simple: in fog, you cannot trust the "feeling" that the oncoming vehicle is far away and moving slowly. You need to reduce your speed so that you can stop within the visible distance, increase distance and gaps, turn on the appropriate lighting and, if necessary, fog lights, remembering that your speed and distance are what you actually control.
Clause 1.10 (term "Insufficient visibility")
Insufficient visibility — road visibility in the direction of travel of less than 300 m in twilight, fog, rain, snowfall, etc.
Clause 1.10 (term "Limited visibility")
Limited visibility — road visibility in the direction of travel, limited by the terrain, geometric parameters of the road, vegetation, buildings, structures, etc.
Clause 2.3 (subclause "b")
To ensure road safety, the driver is obliged to: be attentive, monitor the road situation, respond appropriately to its changes, monitor the proper placement and securing of cargo, the technical condition of the vehicle, and not be distracted from driving this vehicle on the road.
Clause 12.1
When choosing a safe speed within the established limits, the driver must take into account the road situation, the characteristics of the cargo being transported, and the condition of the vehicle in order to be able to constantly control its movement and drive it safely.
Clause 12.2
At night and in conditions of insufficient visibility, the speed must be such that the driver can stop the vehicle within the visible distance of the road in the direction of travel.
Clause 13.1
The driver, depending on the speed, road situation, characteristics of the cargo being transported, and the condition of the vehicle, must maintain a safe distance and a safe interval.
Clause 19.1
At night and in conditions of insufficient visibility, regardless of the degree of road lighting, a moving motor vehicle must have its low or high beam headlights on (in the absence of oncoming vehicles), and a moped must have its headlight on.
Clause 19.4
Fog lights may be used in conditions of insufficient visibility either separately or together with low or high beam headlights.
Rear fog lamps may be used only in conditions of insufficient visibility.
That is, the correct answer is "Yes.", given that according to the definition of the Traffic Rules, fog is a condition of insufficient visibility in which the driver must be especially attentive and choose speed and distance taking into account the limited visibility (to be able to stop within the visible distance of the road), since visual perception of distance and speed in such conditions is unreliable.
In fog, the driver receives incomplete and distorted visual information. Visibility deteriorates sharply, the outlines of objects become "blurred," and landmarks (the edge of the road, markings, the horizon line) become less noticeable. Because of this, the brain evaluates the road situation inaccurately.
When a car is approaching from the opposite direction, you often do not see the actual vehicle clearly, but mainly the diffused light from its headlights. In fog, the light beam is scattered by moisture droplets, so the light source appears "soft" and distant. As a result, the distance to the oncoming car is perceived as greater than it actually is.
At the same time, it is harder to judge the closing speed with oncoming traffic in fog. Due to low contrast and the lack of clear reference points, it seems that the approach is happening more slowly, that is, the speed of the oncoming vehicle (and the closing speed in general) is perceived as lower than in reality. This is dangerous because the driver may mistakenly "leave themselves" less time to make decisions: reducing speed, choosing a safe lateral interval, or refusing to perform a maneuver.
That is why, in conditions of limited visibility, the Traffic Rules require the driver to be especially attentive and to choose a safe speed taking into account visibility and road conditions, as well as to act in such a way as to always have the ability to stop safely within the visible section of the road. In practice, this means that in fog you should allow for an "error" due to optical illusion and not trust the feeling that the oncoming car is far away and moving slowly.
Thus, the correct answer is "Yes," because in fog, due to limited visibility and light scattering, perception is distorted: the oncoming car appears farther away, and its speed (and the closing speed) appears lower than it actually is.