Automotive exterior lighting covers all lights around the perimeter of a motorized vehicle. This can be a car, or truck, or a motorcycle. Automotive exterior lighting is required by law, and there are rigid regulations that must be fulfilled in order for any light function to be road-legal. In addition to the necessity, exterior lights are also considered the jewelry of a car, as lights have evolved from purely technical elements on a car to design highlights that serve as a brand identifier or create a distinct look and catch your the eye on the road.

For illumination purposes, the lighting functions on a vehicle can be separated into two groups: signal lamps and headlamps.

What Types of Exterior Lighting Are There?

Automotive exterior lighting cover the front, rear, and sides of a vehicle, although some special functions may be on the roof as well. For the two main purposes of illumination and signaling, various lighting functions are defined by law in their photometric requirements, position, size, color of light, and many more aspects.

Front exterior lighting includes the:

  • Low beam headlamp (passing beam)
  • High beam headlamp (driving beam)
  • Front fog headlamp
  • Daytime running light (DRL)
  • Turn indicator
  • Front position lamp

In the rear, the lighting includes the:

  • Taillight position lamp (tail lamp)
  • Taillight stop-lamp
  • Turn indicator
  • Reversing light
  • Rear fog lamp
  • Center high-mounted stop light (CHMSL)

Along the sides of a vehicle, there may be:

  • A side turn indicator (fender or side mirror)
  • Side marker lights
Exterior lighting on a car | Synopsys

Special Lighting

In addition to the lighting mentioned, there are other special lights that may be on a vehicle.

  • License plate illumination lights: A special group of lights illuminate the license plate to make sure the legal plates are visible any time in darkness, or visually demanding weather conditions.

  • Signature lights: In addition to the required lighting functions, some countries also allow signature light elements, such as illuminated logos of the OEM brand to be used on the exterior.  

  • Other lights include official authority/emergency light functions for:
    • Firefighters, police, ambulance (blue)
    • Road maintenance
    • Extended size vehicles
    • Hazard transport warning lights (yellow)
  • V2X lights: With the advent of autonomous cars and electrical cars, a very special group of lighting functions has emerged and developed almost silently.  These so-called "vehicle to X" (V2X) lighting functions are a hot topic of interest and research, along with sensor systems (such as cameras, LiDAR, and radar). V2X systems are a means of light-based visual communication to signal to pedestrians or other traffic participants ("X") the status or intention of silent vehicle, or one without a driver.

What Are the Specific Functions of Automotive Exterior Lighting?

Signal lamps are designed to directly shine into the eyes of traffic participants. They are a major element of the visibility of a vehicle and therefore an important aspect of road safety. The purpose of these lamps is to signal a position or action, like taking a turn or braking. They also create an impression of the outer dimensions of the vehicle by correct placement of position lights.

Headlamps (low beam and high beam) what makes it possible for any vehicle to be driven at night. They are designed to illuminate the road ahead so drivers can see where they are going. They create contrast in case any obstacles or other vehicles a in the driving path of you vehicle. 

Low beams utilize a cut-off line in the beam pattern to avoid glaring oncoming traffic. They illuminate mostly the road and a bit left and right of it, but do not shine light into oncoming traffic.

High beams are also called driving beams. These are the headlights with the most range and create the best driver view at night. However, these headlights must only be used when there is no oncoming traffic since it would be blinding to the drivers of the oncoming traffic. For that reason, high beam headlights must be deactivated manually or must be controlled by an adaptive driving beam (ADB) system.

What Problems Does Automotive Exterior Lighting Solve?

Automotive exterior lighting serves to ensure safety in road traffic. Using vehicle lights help the driver illuminate the lane and recognize the road, obstacles and traffic signs. The headlights with the high beam, low beam and fog light functions are primarily used for this purpose.

For drivers on the road, exterior lighting is used to ensure that road users perceive the presence of the vehicle, recognize a driver's intentions, and can react accordingly to them. Daytime running lights, turn lights, and brake lights are used for this purpose.

Why Is Modeling Exterior Lighting on a Car Important?

All exterior lighting of a vehicle are subject to country-specific legal regulations to ensure safe driving. Lighting must not be a glare to oncoming drivers, and signal lights, such as turn signals and stop lights, must be clearly visible. These legal regulations must be considered in the first step of development when modeling an exterior lamp.

In addition to the legal regulations, branding and aesthetics also play an important role. Taillights, for example, offer a very good opportunity to design an individual design or to differentiate between model series during recurring design elements.

How Do You Develop and Model a Headlamp?

The basic workflow is as follows: 

  1. Define optical performance requirements.
  2. Design reflector in LucidShape. Meet optical performance requirements.
  3. Test model and optimize.
  4. Design CAD model in LucidShape CAA V5.

How Can Synopsys Help with Light Modeling?

For modeling the design and real-time simulation of automotive forward, rear, and signal lighting, Synopsys' LucidShape software provides a complete set of design, simulation and analysis tools for superior automotive optical designs.

LucidShape and LucidShape CAA V5 Based offer additional modules that help you to make the development process for automotive lighting even more effective.

  • To demonstrate luminance effects when light sources in a model are illuminated and depict all interactions between system geometry and light sources, use LucidShape's Visualize Module. Designers can then evaluate how a lighting system such as turn signals and brake light will be perceived by the human eye.
LucidShape's Visualize Module - Tail light | Synopsys

Light guide examples in the Light Guide Designer Module for LucidShape CAA V5 Based | Synopsys

LucidDrive complements LucidShape design tools by enabling you to analyze automotive headlamps with various road scenes. It provides a virtual reality in which to perform simulations prior to expensive fabrication and testing.

Explore Synopsys Automotive Lighting Design Software