The Importance of a Headlamp Car

You might be able to imagine a car without headlights, but it was once commonplace to drive cars with lamps that didn’t meet modern standards. Luckily, these regulations help make it safer to operate vehicles at night by reducing visibility and glare.

There are many factors to consider when choosing the right headlights for your car. Here are some of them:

How They Work

Headlights are designed to show you the road ahead. They come in two different forms: low beams (dipped, passing, meeting) and high beams. Low-beam headlights are designed to distribute light in a way that shows you the road ahead while controlling glare for oncoming traffic. High-beam headlights are intended to provide a brighter center-weighted distribution of light but without any control over the amount of light directed towards other vehicles to prevent dazzling them. You can switch between the two using your headlight switch.

Older headlamps used a plain tungsten filament in a reflector to produce the required heat to illuminate the road. Newer headlamps use a high-intensity discharge (HID) bulb to produce the same heat, but with much greater power and brightness. The bulb is housed in a special reflector that contains one or more electrodes. A pulse of high voltage from a battery causes an electrical arc between the electrodes and emits a blue-white glow.

There have long been efforts to devise an effective automatic headlamp system that would choose the correct setting as driving conditions change. Early solutions included resistance-type dimming circuits and tilting of the reflector, which eventually led to dual-filament bulbs in a single reflector with separate low and high beams. More recent developments include sensor-based systems that monitor steering input and vehicle speed to swivel the headlamps in response. These are often called Adaptive Front-Lighting Systems, or AFS.

Light Sources

Many headlamp systems fail to illuminate the road adequately at night, headlamp car resulting in blinding glare for other drivers and pedestrians. Such systems also have a hard time providing sufficient light for drivers to react to unexpected events on the road. At speeds of 55 mph, it takes 1.5 seconds for the driver to react to an obstacle (Jernigan and Kodaman, 2000).

Modern headlamps use either reflection or projection technology concepts for light distribution. Reflection systems utilize large-surface reflectors behind a clear or patterned cover lens to distribute the luminous flux produced by the bulb over the optical axis. Projector-type systems have a small light exit with a characteristic lens that is designed to produce a particular beam shape.

Before the introduction of LEDs, most headlamp bulbs (tungsten, halogen, and HID) used mercury. This substance is toxic to touch and can cause eye irritation in contact with water or dust. The newer Xenon lamps that are now in production do not contain mercury.

Infrared energy emitted by all tungsten and halogen headlamps helps to thaw built-up snow or ice on the lens. This function is not available with LED headlamps. A recent development is adaptive headlamps that automatically select the proper light for driving conditions. They respond to vehicle speed, ambient weather and visibility conditions, road curvature and contour, and oncoming traffic.

Beam Patterns

When a headlamp is activated, it produces a distribution of luminous intensity called a beam pattern. Different patterns produce different illuminations of the road ahead of the vehicle, and their distributions must be consistent with the photometric requirements specified by state motor vehicle administrations. Generally, the higher the wattage of the headlamps, the brighter the light that they produce.

To make high-beam headlamps meet their required intensity, they must be positioned as close together as possible. To achieve this, the bulb in ECE-certified headlamps is rotated within the reflector to position a wedge of its lower half in the arc of the Graves shield. This produces the upsweep or upstep characteristic of the pattern.

Some older cars feature stacked headlamps. In this arrangement, the low-beam headlamp is swung out of the way when the headlamps are activated to prevent dazzle oncoming traffic. This is a popular design on a few Jaguar models, as well as on pre-1968 VW Beetles and 1965 Chrysler and Imperial models.

Some headlamps are covered when not in use by panels that blend into the car’s styling. When the lamps are activated, these panels swivel out of the way, either downward on many Jaguar models or upward on some Jaguar XJ220s and a headlamp car number of Chrysler products of the late 1960s through early 1980s. Other hidden headlamps use a door mechanism actuated by vacuum pots, as on some Ford vehicles of the late 1960s through 1970s such as the 1967 Mercury Cougar, or by an electric motor, as on various Chrysler models of the middle 1960s through the late 1960s.

Glare

A big truck’s headlights can create glare that blinds other drivers. This can cause stress and distraction at best and blindness at worst. It’s estimated that hundreds of fatal night crashes every year can be attributed to glare from oncoming vehicles [NHTSA].

The NHTSA conducted a survey in 2001 where over 4,000 participants were asked to rate headlight glare as their top concern while driving at night. About 30 percent of those who responded said they experienced glare from other cars that was disturbing.

Several factors affect the perceived intensity of a glare source. The ambient illumination level along the roadway can affect whether a given level of glare is considered intolerable (Schreuder, 1969). Headlamp design also influences the degree to which headlamps can cause visual discomfort or disability glare. For example, studies have shown that the glare thresholds for HID, halogen, and blue-filtered halogen headlamps providing different illuminances at the eye are correlated with relative short-wavelength cone stimulation.

Other factors that can impact headlamp glare include the presence of dirt on the cover lenses. A dirty headlamp will decrease one’s own forward illumination while causing the glare from oncoming headlights to increase (Alferdinck and Padmos, 1988). Dirty headlamps also reduce their effectiveness by dispersing the luminous flux of the lamp across a larger area. This can result in a lower level of beam coverage for the low and high beams.