Automotive Electronics

Exterior Lights

Basic Description

There are many lights on the exterior of a typical automobile other than the headlights. For example,

  • Bed Lamps - illuminates the bed of a truck when parked
  • Brake Lights - indicate that the driver of the vehicle has pressed the brake pedal
  • Daytime Running Lamps - make on-coming vehicles more visible when driving during daytime
  • Front/Rear Fog Lamps - aid forward visibility during inclement weather
  • Front/Rear Position Lamps - indicate the presence and the width of a vehicle to others.
  • Front/Rear Turn Signals - indicate to others that the driver intends to change direction
  • Hazard Lamps - flash to make the car more visible when parked on the side of a road or traveling at slow speeds
  • License Plate Lamp - illuminates the license plate
  • Parking Lamps - draw attention to the presence of a stationary vehicle.
  • Reversing Lamps - illuminate the rear area of the vehicle and warn others that the vehicle is reversing

These exterior lights have traditionally employed incandescent bulbs housed in an enclosure with a red, yellow or clear lens; however, incandescent bulbs have a relatively short life and are less efficient than light emitting diodes (LEDs). Because of this, most cars sold today employ LEDs for all exterior lights other than the headlights.

Incandescent bulbs: The oldest electric light source, incandescent bulbs consist of a wire filament that heats up and glows when current passes through it. The bulb contains a gas that displaces all the oxygen surrounding the filament and prevents it from burning up (at least for some time). Most incandescent bulbs have a filament made of tungsten and employ argon gas. Incandescent bulbs operate at relatively low efficiency compared to competing lighting technologies. There is also a trade-off between efficiency and the expected life of the bulb. For the first 60 years of automotive history, virtually all electric lights in an automobile were incandescent bulbs. Today, incandescent bulbs have been largely replaced by other lighting technologies.

Light Emitting Diodes:LEDs are semiconductor devices that emit light. They do not employ filaments or gas. The response time to actuation is extremely fast in comparison with other light sources. LEDs are widely used in modern automobiles particularly for brake lights, turn signals, interior lighting and display lighting. Arrays of white LEDs have recently been introduced for use as automotive headlights. LEDs are highly efficient, durable and relatively compact. LEDs also offer an increase in safety, especially when implemented as tail and brake lights, since they fully illuminate almost immediately after being turned on, whereas incandescent bulbs require some amount of warm-up time to come to full brightness.

Bosch, GE Lighting, Hella, North American Lighting, PIAA, Philips, Sylvania
For More Information
[1] Automotive Lighting, Wikipedia.
[2] Cadillac CTS: Interior and Exterior Lights, YouTube, April 2, 2007.
[3] Car Lighting Makeover Impacts Feel of Safety and Style,, Aug. 16, 2010.
[4] Q&A with Visteon: Automotive Lighting, Just-Auto, March 11, 2011.
[5] Hella Sees Growing Demand For Rear LED Automotive Lighting, PR Newswire, June 22, 2011.
[6] MINI Rocketman Concept - Exterior Design, YouTube, Feb. 2011.
[7] Increasing Trend Towards use of LEDs in Exterior Lighting, Green Car Congress, May 27, 2011.