On how headlights affect safety

For more than a century of the car history, all its components have undergone such significant changes that often modern units have nothing in common with their ancestors except the functioning principle and the name. One of these components is the headlights.

Over the decades, this lighting device has evolved from a banal kerosene lantern and an explosive acetylene torch into a complex device that uses lamps or LEDs, and now lasers. This is not just the desire of automakers to make their cars more technologically advanced and stand out from the competition — working with lighting and, in particular, headlights allows companies to successfully kill two birds with one stone.

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Light as a design element

Oddly enough, but designers more than others welcome new technologies in the field of automotive lighting. This is because each new solution allows them to show more and more imagination in creating of a brand’s identity and cars. Since previously all headlights were round or rectangular and approximately of the same size, it was necessary to make huge compromises in terms of design. Now that there are compact lamps of different shapes, the work of designers has become easier. However, design is not as important to drivers as safety. This is the second aspect that is directly affected by lighting technology.

The rays of safety

On the way to the assembly line, each car passes thousands of tests, where it travels millions of kilometers, in order to make the car reliable and safe. Safety can be passive or active. Passive safety includes the vehicle frame, belts and airbags — in short, everything that comes into operation to protect the driver and passengers during an accident. Active safety comprises systems, doing everything to ensure that the car does not get into an accident at all. When speaking about active safety, people remember numerous driver-assistance systems, but almost no one remembers the headlights. The headlights are one of the most important elements of safety not only for those who are in the car but also outside.

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Everyone who has obtained a driver's license remembers the term «Insufficient visibility» (visibility of the road is less than 300 m in fog, rain, snowfall, etc., as well as at dusk) and the requirement to observe speed, taking into account not only the current limit but also weather conditions, in particular visibility in the direction of movement. Drivers should also always keep in mind that the stopping distance of the car (the distance that the car will pass from the moment the driver detects a danger to a complete stop) should always be less than the distance of visibility —the speed should be chosen so that you can certainly stop when an obstacle appears on the way. When there is no problem with street lighting in cities and on some highways, then, on most roads, you can only rely on the headlights of your car.

No amateur activity

The era of oil and acetylene lamps has become a heritage of history. Nowadays, most cars are equipped with incandescent and gas-discharge lamps, as well as with various technical solutions based on LEDs, which are actively becoming more popular. The more modern the headlights, the better they illuminate the road. Halogen headlights are better than traditional incandescent lamps. Xenon, as well as LEDs, is superior to halogen. It seems to be obvious — if you want to see better and further, install xenon headlights but there are a few nuances.

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Firstly, each model is designed for a specific type of headlights and you cannot just change the usual incandescent lamps to xenon or LED. Secondly, even if you install the latest laser-phosphor lights in your car, your efforts will not be appreciated by the traffic authorities.

The prohibition to replace the light source also applies to LED lamps, which are already produced by many manufacturers in «halogen plinths». LEDs not only look beautiful but also brighter and more durable than halogen lamps due to the fact that it is impossible to improve all the parameters of the latter at the same time. This feature explains their growing popularity. Even if your LED headlamps are from a reliable manufacturer and provide the correct light distribution, installing them instead of the halogen ones is prohibited by law. According to its letter, halogen and LED lamps are different light sources, and the car's headlights are certified for only one of them. Accordingly, a halogen lamp cannot be replaced with an LED lamp and vice versa. Unfortunately, such replacement of lamps will remain illegal until the standards are changed.

The subtle science of automotive lighting

Visually, the headlights do not differ from the usual household bulbs. But in fact, they are more complex in design and must meet a broader and stricter list of requirements of certification bodies.

Let's start with the basics. All lamps are characterized by four main parameters:

  • luminous flux (the measure of the perceived power of light; the SI unit is the lumen (lm))
  • luminous intensity (intensity of light emitted in a certain direction, measured in candelas (cd))
  • illuminance (the amount of luminous flux per unit area, measured in lux (lx));
  • luminance (the intensity of light emitted from a surface per unit area in a given direction; the SI unit is candela per square meter (cd/m2)).

The most important thing for the driver is illuminance — the amount of light that falls on the road and improve visibility. So, manufacturers of headlights pay special attention to this parameter. Car owners often prioritize luminous flux and focus on the number of lumens, but this is an erroneous approach. This is a really important indicator for an ordinary household lamp, because it should shine in all directions. However, headlights should emit the maximum light in one particular direction, and therefore it is the level of illuminance that comes to the fore.

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Structurally, the halogen lamp is not too sophisticated, but this simplicity is deceptive. The correct light distribution is primarily affected by the location of the tungsten filament in the bulb — the position of this element in low-quality lamps may differ markedly from the set standards. Because of this, the car owner, who has saved on headlights, may not even hope for a clear cut-and-shadow border and uniform lighting of the road without blinding oncoming drivers. The quality of light depends not only on the quality of the lamp assembly but also on the quality of the tungsten filament and gas in the bulb.

Gas (bromine or iodine vapors) allows to avoid the deposition of tungsten particles on the lamp bulb — the filament when heated releases tungsten atoms, which tend to end up on the lamp glass due to temperature differences. If there is no gas, the bulb will turn black very quickly and the lamp will lose its effectiveness. Bromine or iodine vapors enter into a reversible reaction, creating compounds that do not accumulate on the glass but allow the tungsten atoms to return to the filament — the working temperature of the spiral can be higher, increasing the brightness and durability of the lamp.

The process is simple, but the very operation principle of the halogen lamp forces engineers to organize priorities — get a brighter light or increase durability. You cannot do both at the same time. Therefore, there are different lamps with their own advantages.

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In pursuit of halogen perfection

In order to increase the service life, a more concentrated gas is pumped into the flasks — more bromine or iodine atoms increase the chance of «meeting» the tungsten atom, and then returning it to the filament. This directly affects how long the lamp will remain effective. However, these measures lead to a significant increase of the pressure inside the flask, what makes manufacturers suffer from headaches. Osram, for example, uses quartz glass instead of refractory glass in its lamps with added characteristics to cope with pressure. Also, the light sources additionally protect against vibrations that are unavoidable while driving the car.

Increasing the brightness of the halogen lamp is also not given just like that. More than a thin tungsten filament is used here. This simultaneously increases both the number of filament turns and the strength of the current passing through it, which provides more light at the output. But because of this, the lamp burns out faster, so do not be surprised that your Night Breaker Laser +150% will have to be changed after 3-4 months of active use. In order to somehow extend the life of super bright halogen lamps, Osram adds xenon to the gas mixture, which effectively concentrates heat near the filament and due to the size of its atoms does not allow the tungsten atoms to fly away from the filament too far, thereby slowing its wear. The added brightness also imposes the need to adjust luminous flux, so you can notice a special blue light filter on the bulb, which allows to bring the lamp in compliance with all certification standards.

If we speak about white lamps, their feature is a higher color temperature compared to conventional halogen lamps (about 3200 K) — it is 4200-5000 K. This makes the light of the lamp closer to natural white daylight, in contrast to the white-yellow color of a standard lamp. You can't just increase the color temperature of halogen lamps — this requires a special filter on the bulb, which allows to make the standard yellow color of the tungsten filament more white — the darker the blue color of the lamp filter, the whiter the light. But even here there was a compromise: the blue filter significantly reduces illuminance, so you need to increase the brightness, and this leads to a reduction in durability, as we discussed above.

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But there are limits. For example, you cannot make a 6000-K halogen lamp because you will need an even darker filter, and it is impossible without increasing the lamp's power — and this is no longer allowed by law. Therefore, a whiter color is the prerogative of LEDs.

Scientific miracle in the service of drivers

If you think that everything is lost and the only way to see behind the wheel is to buy a new car, then you are mistaken. There are thousands of vehicles driving around the world that are designed to use a specific type of headlights. Manufacturers of headlights are well aware of drivers ' problems and do everything to ensure that driving is safe in any weather.

German company Osram is a very good example. It has been working in the field of lighting technology for more than a century, being one of the world's largest manufacturers of lighting equipment. Many cars, trucks, motorcycles, and scooters are equipped with headlights made by this manufacturer. It is quite logical that, delivering their products to the assembly plants of the world’s car manufacturers, the specialists of the German company were also thinking about how to make life of car owners easier.

Given the many factors that need to be constantly kept in mind when developing new solutions, the work of engineers is not easy. But as a result of scientific research and technical know-how, three series of Osram’s halogen headlights appeared: Night Breaker Laser, Cool Blue Intense and Ultra Life.

The Night Breaker Laser lamps were created to «destroy the darkness» — and this is not just a beautiful name but a short description of the capabilities of these lamps. The halogen lamps provide with 150% more brightness (beam up to 150 m), and the xenon lamps — 200% more brightness (beam up to 250 m). In addition, the emitted light of the Night Breaker Laser lamps is up to 20% whiter, and this is important for preventing eye strain —the natural lighting of the headlights allows you to strain your vision less, increasing safety on the road.

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The company has also developed a line of the Cool Blue Intense lamps with a neutral white light at a temperature of 4200K. Headlights with such lamps are not only 20% brighter than conventional halogen ones, but also provide more natural lighting. The Ultra Life series has been created for those who value the durability of lamps — it works four times longer than the average halogen lamp. In figures, this is about 100.000 km of mileage (the average annual mileage is 14.259 km and the lights are on 60% of the time), which is important for those who often go on long trips and are not ready to risk their cars’ reliability and safety on the road.

Taking care of everyone

The efficiency of the new lamps was not sacrificed to versatility. Osram’s solutions are first of all certified and meet all world standards, and they are suitable for any car. «Any» in the case of the German lamps means really any, regardless of the brand, model and age of the car. One replacement of the lamp without any modifications (which is prohibited, once again, by law) can improve the quality of the headlights 2-3 times.

It is much more reasonable to change the lamps in advance and see the light on the road, than to spend money on repairing the suspension due to a missed pit in the dark, narrowly avoiding an accident on an unlit highway.

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