Fog lights: designation in the car and rules of use

At dusk or when caught in thick fog, every driver is faced with the need to quickly turn on additional lighting. However, in a hurry or when driving a new, unfamiliar car, it is easy to confuse the keys and turn on the high beams instead of the fog lights. This not only blinds oncoming drivers, but can also be useless in dense fog conditions, since high beams tend to reflect off water droplets, creating a “wall of light.”

That's why designation of fog lights in a car should be known to every motorist before leaving the road. Manufacturers use standardized pictograms that are regulated by international standards, but their location and operation logic can vary significantly depending on the make and model of the vehicle. Understanding these differences is key to driving safely in adverse weather conditions.

In this article we will look in detail at what the front and rear fog light icons look like, what is their fundamental difference and how to use them correctly so as not to violate traffic rules and ensure maximum visibility. We will also touch on technical implementation issues and common mistakes that even experienced drivers make.

Standardization of symbols: what PTF icons look like

All modern cars produced for the general market are required to follow the same ISO standards, which regulate the appearance of controls. Designation of fog lights on buttons and rotary switches has a characteristic feature that distinguishes it from the main light symbols. The main visual marker is a wavy line crossing the rays of light, which symbolizes the ability of the light stream to “pierce” the fog.

There are two main types of pictograms that need to be distinguished: for the front optics and for the rear light. Front fog lights are indicated by a symbol where the rays are directed down and to the left, and the headlight itself (semicircle) is located to the left of the vertical line. It is important that the rays in this icon are always green on illuminated panels, which indicates the normal operation of the lighting system.

The rear fog lamp has a radically different designation to eliminate confusion. The beams on this symbol are directed straight and horizontal, and the headlight is often depicted to the right of the vertical line or has a different body shape. The color of the indicator on the dashboard when the rear fog light is turned on is always red, which is a direct indication of high brightness and the danger of dazzling drivers of cars behind.

Important to note: On some budget models or in cars with simplified equipment, individual buttons may be absent, and control is carried out through the on-board computer. In such cases, the symbolism is reproduced on the display, but the logic remains the same - look for a wavy line.

Differences between front and rear fog lights

Many beginners mistakenly believe that fog lights are just additional light bulbs that can be turned on all at once. However front and rear fog lights perform diametrically opposed functions and have different requirements for installation and use. Front optics are designed to illuminate the roadside and the lower layer of the atmosphere in front of the hood without creating glare.

The rear fog lamp, in turn, serves as a high-brightness brake light. Its task is to make the car visible in traffic with zero visibility. In clear weather, turning on the rear fog light can cause discomfort to drivers following you, and even provoke an emergency due to a false perception of light intensity.

According to the rules, rear fog lights can only be installed in a pair (two pieces) or one (if it is the left or center light), but their brightness is strictly regulated. The headlights must have a clear cut-off line so as not to blind oncoming traffic, but at the same time effectively illuminate the markings at the edge of the road.

• 🚗 The front PTFs have an asymmetrical light beam directed to the right (for right-hand traffic) to better illuminate the roadside.
• 🛑 The rear PTFs burn with a constant bright light and do not have a complex beam shape; their goal is maximum visibility.
• 🔦 The scattering angle of the headlights is wider, which allows you to cover a larger area near the front bumper.

Location of controls in different cars

Finding the button to turn on the foglights can turn into a quest if this is your first time driving a particular car. Manufacturers are not required to place light controls in specific locations, although they adhere to general ergonomic principles. Most often PTF switch located on the dashboard to the left of the steering column, on the turn signal lever itself or as part of the rotary light control.

VAG cars (Volkswagen, Audi, Skoda) and many European brands use a rotary switch on the dashboard. To turn on the fog lights there, you often need to pull the central part of the regulator towards you (the first click is for the front, the second is for the rear). In Asian cars (Toyota, Honda, Kia) there is often a separate button next to the hazard warning light button or on the steering column switch.

Modern premium cars are increasingly abandoning physical buttons, transferring control to the multimedia system menu. This creates certain inconveniences, as it requires diverting attention from the road to find the desired item in the menu Settings → Light → Fog lights. Such systems often implement an automatic mode, but it does not always react correctly to dense fog, requiring manual intervention.

Interesting fact: in some models (for example, old BMW or Mercedes), turning on the rear fog lights is possible only when the main headlights are active, which is implemented at the electrical circuit level to prevent errors.

Why is it impossible to turn on PTF without dimensions in some cars?

This is a safety and standards requirement. The logic is this: fog lights are an additional light that cannot work autonomously. If only the fog lights are turned on without the side lights, the car becomes poorly visible in profile, which increases the risk of a side collision.

Dashboard display: green and orange

After pressing the button, the driver must verify that the system is activated. For this purpose it is used indicator on the instrument panel. As mentioned earlier, the color of the glow is critical. A green icon with beams pointing down and to the left confirms the operation of the front fog lights. This is a normal operating mode that does not require immediate shutdown when conditions improve, although it is undesirable in the city.

The orange or yellow indicator (sometimes red) indicating the rear fog lights requires more careful attention. A light bulb with rays directed to the right indicates that a powerful red light is burning behind. On a clear night or on well-lit city streets, this light will dazzle drivers behind you, causing irritation and reducing overall safety.

The absence of indication when the button is on may indicate a malfunction. This could be a burnt-out lamp, poor contact in the connector, oxidation of the wiring, or a blown fuse. In modern cars with a self-diagnosis system (CAN bus), information about a burnt-out lamp can be displayed as a text message on the on-board computer display.

Indicator type	Color	Meaning	Driver action
Front PTF	Green	Headlights on	Control use in the city
Rear PTF	Orange/Yellow	Flashlight on	Turn off when visibility improves
System error	Flashing/Red	Lamp failure	Check the integrity of the optics
Auto mode	Green (AUTO)	Light sensor active	Keep the sensor clean

Rules of use according to traffic rules and technical regulations

The use of additional light is regulated by paragraph 19 of the Road Traffic Regulations. Fog lights can be used independently at night on unlit sections of roads, as well as during the day instead of low beam (although this is not always recommended due to the shorter lamp life and narrow beam). However, combined use with high beams is prohibited.

Rear fog lights may only be used in conditions of poor visibility (fog, rain, snow, smoke). Using them in clear weather is a violation for which a fine is imposed. The main reason for the ban is excessive brightness, which under normal conditions is perceived as a stop signal, confusing road users.

The Technical Regulations of the Customs Union (TR CU 018/2011) establish strict requirements for the quantity and location of installation. A passenger car may be equipped with no more than two front and no more than two rear fog devices. Installing xenon lamps in headlights not intended for them (usually halogen PTFs) is also illegal and dangerous, as it blinds oncoming drivers.

⚠️ Attention: Installing xenon or high-power LED in conventional halogen fog lights without replacing the lens and washer will entail deprivation of rights for a period of 6 months to 1 year (Part 3 of Article 12.5 of the Code of Administrative Offenses of the Russian Federation).

Typical faults and their elimination

Even when used correctly fog lighting system may fail. The most common problem is contact oxidation. Since PTFs are located low to the ground, they are constantly exposed to water, reagents and dirt. Moisture penetrates the connectors, causing corrosion and loss of contact.

The second most common cause is lamp burnout due to vibration or power surges. Halogen lamps are sensitive to shaking, so when replacing, avoid touching the bulb with your fingers (oil from the skin leads to local overheating of the glass and rapid failure). If you have LED modules installed, they usually last longer, but if they break, they often require replacing the entire assembly.

It's also worth checking the fuses. In a car's electrical circuit, PTF circuits are often protected by separate fuses, which are located in the mounting block under the hood or in the passenger compartment. If both headlights stop lighting at the same time, the problem with a 90% probability lies in the fuse or relay, and not in the lamps.

FAQ: Frequently asked questions

Is it possible to drive with only the fog lights on without low beams?

According to traffic regulations, at night on unlit sections of roads it is allowed to use fog lights separately from the low beam. However, during the day, PTF can be used as a replacement for low beam, but not vice versa (it is impossible to turn on PTF without dimensions or low beam in the dark, unless this is specifically permitted by the design for this mode).

Why does the fog light error indicator light up even though the bulbs are intact?

This may indicate poor contact in the connector, oxidation of the socket, or the use of non-standard power lamps, which is why the on-board computer records a discrepancy in the circuit resistance. It is also possible that moisture gets inside the headlight, causing a short circuit.

How often should you turn on the rear fog lights?

Only when visibility is less than 300 meters (conditionally: when you do not clearly see the junction or object ahead). In normal rain, when the wipers are working, but visibility is good, turning them on is not necessary and is even harmful to others.

Is it possible to install xenon in fog lights?

Only if the headlight is marked “D” and is structurally designed for gas-discharge lamps, and is also equipped with an auto-corrector and washer. Otherwise it is illegal and dangerous.

⚠️ Attention: When buying a car second hand, be sure to check the operation of the PTF. Often, sellers hide wiring problems by simply unscrewing the non-working lamps so that the error indicator does not light up on the panel.