Automotive lighting improving safety for everyone

From gas lamps to xenon lights, vehicle exterior lighting technology keeps evolving.

electrical vehicle lighting automotive lighting xenon lighting repair shop training technician training automotive aftermarket "Two lamps fed by either petroleum or electricity are essential on the mudguards. These small lamps are quite adequate in city traffic to comply with police regulations, large headlamps would only be a hindrance in city traffic as they dazzle both horses and people. Electric lamps with a switch on the mudguard are effective; there are 4- and 8-volt versions which are connected to one or two batteries. These lamps are not adequate for country journeys at night, however. It is advisable to mount two headlamps on the front of the frame, to the right and left of the radiator, and these are best powered by electricity or compressed acetylene gas carried in steel flasks."

This is a quote from The Modern Automobile, circa 1914, which was regarded as a standard reference for automobile design in its time. Even then, engineers were faced with the need to illuminate the roadway without blinding oncoming drivers. During this time in automotive history, lighting was often provided by a combination of electric lights and gas lamps (petroleum or acetylene). In 1908, a mechanism was invented that used a lever operated cable to "dip" the gas flame away from the focal point, resulting in the first high/low beam switch.

Electric lighting was restricted by the batteries of the era, until Bosch developed the first dynamo powered headlights, fitted as an accessory to cars of the age. Electrical systems were not mature enough to make electric lighting practical until the 1920s.

In 1924, the "bi-lux" bulb was invented, a twin filament bulb which contained the low and high beam in one reflector and producing two distinct lighting patterns. This was the standard until the mid-1960s when the halogen bulb was introduced.

Not only did bulb technology reach new levels, so did reflector technology. New computer designs allowed smaller housings, acting more like a projection lens rather than a mirror reflector. This allowed designers to precisely focus the lighting pattern for better nighttime visibility.

The next major improvement in lighting was the development of the xenon bulb, which uses xenon gas in a quartz shell, with some trace metallic salts added. A short 28,000-volt discharge results in a plasma arc between the lamp's electrodes. This arc is stabilized at about 85 volts and takes the place of the filament used in other designs.

This design produces twice the light at 35 watts as a halogen bulb does at 55 watts, resulting in less electrical load for the car to carry. Due to the intensity of the lights, these systems generally are coupled with self-leveling headlight units that constantly adjust the lighting pattern relative to the road, vehicle load, acceleration/deceleration and road inclination. In 1999, bi-xenon lighting was introduced, meaning that xenon bulbs generated the light source for both the main (high) and dipped (low) beam.

Safety: the Driving Force

A 2004 Department of Transportation (DOT) study shows that 20 percent of all fatal accidents occurred between midnight and 6 a.m. Visual perception, responsible for 90 percent of the traffic information we take in while driving, can be reduced to as little as 4 percent with poor nighttime visibility weather conditions.

Adaptive Front Lighting Systems (AFS) have been in development since the beginning of this century. These systems use information provided by the vehicle speed sensor, yaw rate sensor and/or steering angle sensor to alter the beam direction from straight ahead to approximately 15 degrees left or right to correspond with vehicle direction and better illuminate the inside edge of any curve in the roadway. These systems improve visibility by nearly 90 percent.

One Ford concept AFS system incorporates LED lighting with a halogen main beam. The LEDs light sequentially and can be varied in intensity to illuminate the curve at a rate matching the vehicle's speed and rate of turn. (Another unique concept worth mentioning is a solar-powered headlight that stores energy during the day for use that night.)

AFS was further improved by the addition of cornering lamps that can rotate up to 90 degrees from the vehicle centerline, adding visibility to the inside of intersection turns or parking lot maneuvers. This system does not operate except at slower speeds, or when steering wheel rotation speed is higher than normal.

Another recent advancement in exterior lighting was created by Hella, and currently is offered as an option on Mercedes-Benz models for sale outside of the U.S. The Intelligent Lighting System uses a third servo motor to rotate a drum inside the light assembly, altering the light pattern to meet specific needs.

There are five lighting modes available in this system. Country mode improves lighting to the sides of the vehicle's path, while Motorway mode extends the range of the light pattern by another 165 feet by increasing the power of the bi-xenon lighting system from 35 watts to 38 watts. Expanded Fog Light mode lowers the driver's side low beam pattern to reduce light reflection and self-glare; Active Light mode that works like other AFS systems; and Cornering Light mode that angles the beam up to 65 degrees from the center line for low speed turn illumination.

While these newer improvements surely added to the driver's ability to see the road, they still do not provide maximum illumination or prevent blinding oncoming drivers when the main beams are in use. Hella and Mercedes introduced an innovative answer to that problem in the new E-class, called Adaptive High Beam Assist (AHBA).

When the driver selects the "auto" lighting function, and vehicle speed exceeds approximately 35 mph, AHBA takes over. A windshield-mounted camera scans the road ahead, and the software is able to distinguish between headlights, taillights, street lighting or lane markers at a distance of up to nearly half a mile. Based primarily on this information, the variable reflector can alter the dipped beam pattern for each individual headlight to keep the cone just short of other vehicles.

Low beam can be ranged from 200 to nearly 1,000 feet, and transitions automatically to high beam if the road ahead is clear with no need for the driver to operate a switch. Using this system, the main beams are in use nearly 25 percent of the time, versus only 8 percent when high beam has to be selected manually. Lighting is updated every 40 milliseconds, and the system doubles the visual recognition range of standard low beams.

Not Just For the Front

One new idea we may see on our shores soon is "smart" rear lighting. These designs use LEDs, and the amount of braking force applied by the driver will be reflected in the intensity of the stop lamps seen by the driver behind. In the case of an emergency stop, all the rear lights will illuminate and flash at a specified frequency of 4.0 ± 1.0 Hz.

Add in innovative software to the current camera systems, and the two cars can communicate without human involvement. This can lead to further development of emergency braking programs that will lead to even more lives saved.