This year’s Spring Festival transportation encountered rain, snow, freezing and foggy weather, which brought a lot of inconvenience to everyone’s travels. Road traffic safety risks increased. How to drive safely in bad weather, in addition to the consensus of “drive carefully and slow down”, Also use lights correctly, especially the use of fog lights.
In foggy weather, you should turn on the front and rear fog lights instead of the hazard warning flashers (double flashes).
Please see below how to turn on the fog lights
What is the function of fog lights?
Don't be too quick to look at me with disdain. Many drivers really can't answer. Here are the unified answers: 1. Supplement lighting in rainy and foggy weather; 2. Let people around you notice your presence. The first point is easy to understand, but many people are not aware of the second point. Therefore, the next few questions: when to turn on the fog lights, when not to turn on, and what are the reasons... naturally cannot be answered. Therefore, the following focuses on answering these questions:
What is the principle of fog lights?
[The parallel light of the headlights hits the fog, forming the above "Tyndale effect", but the fog lights can crack it very well]
Fog lights are used in low visibility conditions and must have sufficient penetration. Before talking about the principle of fog lights, let’s first take a look: Air is an aerosol, filled with various “impurities” such as tiny water droplets and suspended particles. The light emitted by the headlights must pass through these impurities to reach the ground. Since it is an aerosol, the light from the headlights will inevitably produce the "Tyndale effect" when passing through it, which is the phenomenon of parallel light diffracting into a bright light column when passing through the air. On a good day, these "impurities" are harmless and we won't notice them. However, it is different when visibility is low. The light of ordinary headlights is concentrated together, and it is difficult to penetrate dense fog and water vapor. When high-brightness lights hit the fog, the Tyndall effect is very obvious. The result is that the vision is completely white and nothing can be seen about the road conditions. This is why high beams cannot be used in heavy fog. The strong and concentrated light of high beams can turn the fog ahead into a bright "wall".
The principle of the "Tyndall effect" is that the wavelength of visible light in certain bands coincides with the aerosol particles, causing diffraction, so that parallel light cannot pass through in a straight line. Therefore, the best way to weaken the "Tyndall effect" is to keep the light source away from these bands as much as possible. The wavelength of fog lights is relatively long, which can minimize diffraction and allow more effective light to pass through dense fog and tiny water droplets. At the same time, the light of fog lamps is divergent rather than parallel, and does not converge like headlights. If the light rays do not converge together, the Tyndall effect will not be amplified.
To put it simply, fog lights are specially designed to have two major advantages: first, strong penetration and high recognition; second, there is almost no Tyndall effect, and the light will not hit the fog and block the line of sight. It can also illuminate the nearby ground. This is the key to distinguishing fog lights from other car lights.
Why are the colors of the front and rear fog lights different?
Regardless of the front or rear fog lights, the principle is actually the same. So why are the front and rear fog lights different colors? This is the so-called "concrete analysis of specific situations."
Let’s talk about front fog lights first. In the last century, car front fog lights were generally yellow because red and yellow light have longer wavelengths and stronger penetrating capabilities. Red has been conventionally used as a taillight, so yellow has become the first choice for fog lights. . However, this concept no longer applies today. We know that fog lights in new cars now generally use white light sources. On the one hand, it is for aesthetics. On the other hand, the halogen headlight source is white. To get yellow light, you must use a yellow lampshade to filter out the yellow light. In the end, you may only get about 30% light transmittance. In this case, the actual power of the fog lights is greatly reduced. The manufacturing technology of halogen bulbs is much more advanced than before. There is much less "noise" in the light source than in the past, and the Tyndall effect is not obvious. Therefore, using a white light source is a choice that takes into account both aesthetics and actual power.
Then why aren't the rear fog lights white? Because the reversing lights were already "first on the scene", in order to avoid misunderstandings, red was used as the light source. After all, it is not a big problem to regard the rear fog light as a tail light or brake light (the three types of lights all have the meaning of "keep the distance between the car and stay away from me"), and the conditions for turning on the rear fog light are met, which is why the tail light cannot penetrate When seeing through thick fog, the rear fog lamp should be a supplement to the tail lamp. If a white light source is used, in a foggy day, the driver behind will use the reversing light as the rear fog light and "follow" the car without knowing where it is going, which is very likely to cause a rear-end collision.
In order to solve the problem of insufficient light transmittance and to distinguish it from ordinary tail lights and brake lights, the brightness of the rear fog lights is very high. The power of the halogen fog lights is the same as the brake lights at 21W (LED tail lights are a separate matter, but the brightness is also Restricted by regulations), the difference is that fog lights are relatively regular scattered light sources, which look very dazzling when visibility is high. The brake lights are irregular scattered light sources, and they will not dazzle the driver when they are normally lit. So, again, the brightness of the rear fog lamp is just right when used in rainy and foggy weather.
When to use fog lights and when not to use them?
[When visibility is less than 200m, fog lights should be turned on, but few drivers comply, and "ghost cars" run rampant everywhere. 】
Due to this special principle of fog lamps, it has a certain range of use. First of all, the light source of fog lamps has no directionality and looks similar from all angles. When separated by heavy fog, the light intensity is just right. In this way, the fog lights play a role in improving visibility. When the visibility returns to normal, the high brightness and scattering characteristics make the fog lights a very dazzling light source. At this time, the fog lights should be turned off without hesitation.
Secondly, in rainy and foggy weather, fog lights cannot be used at any time. Regarding its use, let’s take a look at the official statement from the Ministry of Public Security:
When visibility is between 200m and 500m, low beam lights, width lights and tail lights must be turned on, the speed must not exceed 80kmh, and a driving distance of more than 150m must be maintained with the vehicle in front of the vehicle driving in the same lane;
When visibility is 100-200m, fog lights, low beam lights, width lights and tail lights must be turned on, the speed must not exceed 60kmh, and a distance of more than 100m from the vehicle in front must be maintained;
When the visibility is 50-100m, the fog lights, low beam lights, width lights and tail lights must be turned on, the speed must not exceed 40kmh, and the distance from the vehicle in front should be more than 50m.
When visibility is less than 50m, the public security and traffic control departments will take traffic control measures to close part or all of the highway in accordance with regulations.
In other words, fog lights only come into play when the visibility is less than 200m. There are two reasons: first, when the visibility is greater than 200m, the headlights, width lights, and taillights can already provide sufficient lighting and warning effects; second, the fog at this time can soften the fog lights, and the visibility is poor, requiring fog. lamp as supplementary lighting.
Which is more "conspicuous", rear fog light or double flashlight?
When encountering bad weather on the highway, many drivers can’t wait to turn on their double flashers. Many people even have such a mentality that they turn on the double flashing lights and think that they are the "privileged car" that attracts thousands of people's attention. They frequently merge and weave in the traffic flow at high speed in strong winds and heavy rains. We don’t take the time to condemn this behavior, but there are three questions worth discussing: 1. Are double flashes suitable in rainy and foggy weather? 2. When the dual flashers are turned on but the fog lights are not turned on, when will the fog lights be turned on? 3. What should I do when changing lanes when double flash is activated?
The double flashing lights are bright yellow, and the color is close to the fog lights of the past. It makes people feel that everything will be fine when driving it in rainy and foggy weather. In fact, the dual flashlights only look "conspicuous", and the actual effect is not comparable to fog lights at all. First of all, it does not have a special design like a fog lamp, and the light it emits is irregularly scattered like a taillight, rather than a regular radiant pattern; secondly, its brightness is far less than that of a fog lamp.
Therefore, when you drive through thick fog or encounter heavy rain on the highway, the correct approach is to maintain a reasonable speed and turn on the low beam and front and rear fog lights. In addition to making your own vision as good as possible, it also makes it easier for others. Aware of your presence and the distance between you. But be sure not to turn on the high beam. When the high beam shines in the fog, the white flowers will be more dangerous. And in such weather conditions, you are obliged to reduce the speed to a range suitable for using low beam headlights. Driving on the road is actually a process of interaction between every driver.
Proper use of lights can significantly reduce traffic accidents. Being seen by others is as important as seeing the road yourself. This is an unbreakable truth.
