LEDs were first applied to automotive lighting in Centre High Mount Stop Lamps (CHMSL), beginning in the early 1990s. Adoption of LEDs for other signal functions on passenger cars has been slow, but is beginning to increase with demand for the technology and related styling updates. The 2007 Audi R8 sports car uses two strips of optically-focused high-intensity LEDs for its Daytime Running Lamps. Optional on the R8 in ECE markets is the world’s first LED headlamp made by AL-Automotive Lighting. The low and high beams along with the position (parking) lamp and front turn signal are all realized with LEDs. The Lexus LS 600h features LED low beam, position and sidemarker lamps in North America, and the 2009 Cadillac Escalade Platinum uses LEDs for the low and high beams, as well as for the position and sidemarker lamps.

The commercial vehicle industry has rapidly adopted LEDs for virtually all signaling and marking functions on trucks and buses, because in addition to the fast rise time and concomitant safety benefit, LEDs’ extremely long service life reduces vehicle downtime. Almost all commercial vehicles use exterior lighting devices of standardised format and fitment, which has cost-reduced and sped the changeover.

The linear packaging of the neon light source lends itself to the linear packaging favored for many CHMSL installations, and neon lights offer the same nearly-instant rise time benefit as LEDs. However, neon tubes require an expensive and relatively power-hungry ballast (power supply unit), and as a result, neon lights have not found significant long-term popularity as sources of light for automotive signaling.

Xenon is currently the lamp used in single-source lighting systems being developed for automotive use. In these systems, a single light source sends light via optical fibers to wherever it is needed in the automobile. This development, known as distributive lighting, is already appearing in the interior lighting features, for example the Ford Mustang’s interior lighting. In an expanded system, the light could be channeled to the side mirrors for example, which would act as forward driving lights that could be made to swivel in position with the car as it turns. The headlight pattern would not be limited to individual overlapping beams, but could be chanelled by electronic controls of the fiber optics to provide optimum visibility over an extended range of driving conditions including fog, dust or snow. Individual lamps would not be needed, just a mounting point for the optical fibers running back to the single light source and computer controlled for colour, intensity and continuity.

LED light sources are beginning to appear increasingly as interior convenience lights in various locations as the technology becomes more widely used, especially with finely focussed lighting on console control surfaces and in cabin storage areas.

There may be additional map lights that are aimed at specific passenger positions, that allow for reading without particular glare distraction to the driver. Some vehicles have approach lighting (puddle lights) integrated into the exterior mirrors or lower edges of the doors, as well as activating interior lighting, that is activated via key fob. Many cars have lights in the trunk (or boot), the engine compartment, and the glovebox and other storage compartments.

Most instruments and controls on a dashboard in modern vehicles are illuminated in some fashion when the headlamps are turned on, and the intensity of light can be adjusted by the driver for comfort. Saabs feature an aerospace technologies-derived “night panel” function which shuts off all interior illumination save for the speedometer (unless attention is called to a critical situation on another gauge) to improve the driver’s night vision.

Some jurisdictions, such as the US states of Oregon and Idaho, permit vehicles to be equipped with auxiliary rear signal systems displaying green light when the accelerator is depressed, yellow light when the vehicle is coasting, and red light when the brake is depressed. Such systems have in the past been sold as aftermarket accessories, but are today seldom seen in traffic.

Research and development

The US National Highway Traffic Safety Administration, among other bodies, has commissioned studies of these and many other vehicle signal systems and configurations, in an effort to determine the most promising avenues and best practices for enhanced crash avoidance via optimised vehicle conspicuity and signal lighting systems.