Home » Automotive » Intelligent Signal Displays: The New Language for Vehicle Intent
Software-defined exterior lighting is becoming a communication interface for conveying vehicle intent, brand identity, and autonomous capabilities, while staying inside safety, EMC, and regulatory standards.
From Simple Signals to Expressive Storytelling
Imagine standing at a crosswalk behind a modern electric vehicle (EV) and noticing its rear lights gently widen as a cyclist approaches, seeing the turn signals animate at different speeds, or watching a soft, pulsing band that tells you the car is parking itself. These are no longer mere lamps, the lights are not just on or off; they are acting as a software‑driven interface that communicates what the vehicle is doing.
High-end vehicles are already embracing expressive lighting for animated welcome sequences, configurable signatures, and proximity alerts that turn brand identity into something alive and recognizable. Lamp makers now provide uniform optics and robust housings that support reliable animations and crisp icons, while illuminated front panels and controlled micro-projections point to what is coming next within regulatory boundaries. Increasingly powerful, AI-enabled cockpit systems are pushing expectations for how vehicles communicate inside and out.
【Download】Electric Drive Control with Adaptive Computing
That is the essence of Intelligent Signal Displays; software‑controlled exterior lighting systems that use segmented OLEDs, LED matrices or micro‑projectors to deliver clear, short visual cues. These cues communicate safety intent, support automated driving functions, and express brand character. The potential benefits include safer roads and greater user trust, but the core challenge is balancing creative expression while complying with regional electrical, optical, EMC, and regulatory requirements to protect all road users (Figure 1).
Fig 1. ISD for Software Defined Lighting
Defining Intelligent Signal Displays
For this article, an Intelligent Signal Display (ISD) is any exterior lighting system that uses software to go beyond simple illumination, providing dynamic or symbolic cues. For example, a vehicle’s LED tail lamps can adjust their signatures to emphasize warnings, highlight proximity to an object, or display simple alert icons. Larger LED matrices and light bars enable short pictograms or directional highlights with high brightness and durability. Some systems even use micro-projection technologies, such as digital light processing or micromirror devices, to project symbols onto the pavement, for example, a yield indicator during a low-speed maneuver.
From a design perspective, these displays are distributed across the front, rear, and sides of the vehicle and are synchronized through networks like Controller Area Network (CAN), Local Interconnect Network (LIN), or Ethernet. Each module has its own LED drivers that handle pulse-width modulation (PWM), diagnostics, and protective functions, while software dynamically adjusts the lighting patterns to reflect the vehicle’s current state. This architecture allows the vehicle to communicate its intent clearly to its surroundings through synchronized, adaptive lighting effects.
Why Are ISDs Emerging Now?
As vehicles become more autonomous, trust and acceptance depend on how clearly they communicate their actions and intentions. Human-centered studies show that when people can easily understand what a vehicle is doing and what it plans to do next, they feel safer and more comfortable around it. The external human-machine interface (eHMI) defines the messages road users should receive, and ISDs are the lighting-based implementation that delivers those messages on the vehicle exterior. ISDs are the lighting-based implementation of that concept, using segmented or matrix LEDs on the vehicle exterior to present those messages in a clear, structured way.
Advanced driver assistance systems and automated functions must express visible intent to other road users, not just to connected vehicles and infrastructure. Even as vehicle-to-everything (V2X) communication expands, many pedestrians and cyclists will remain outside this radio network and will continue to rely on visual cues. Standardized light signals for states such as yielding, waiting, or active remote parking, rendered through ISDs, help reduce hesitation in mixed traffic by converting perception, planning, and V2X outputs into simple, device-neutral patterns. In motion, these patterns typically favor icons and clean motion cues rather than text to maintain clarity. (Figure 2)
Within this architecture, V2X provides low-latency intent data that allows vehicles to trigger proactive lighting behaviors, such as hazard alerts or cooperative cues. V2X feeds this data to the Automated Driving System (ADS) core, which then drives the ISD pattern engine. ADS indicator lamps sit at the center of this strategy as the safety critical core of ISD. They are based on emerging SAE J3134 and UNECE AVSR/GRE concepts for ADS indicator lamps, which currently focus on indicating when the automated driving system is engaged. By establishing a compliant and trusted baseline, these ADS indicators create the foundation on which richer, more expressive ISD behaviors can evolve as standards and shared semantics mature.
Fig 2. V2X and ISD Informing Pedestrian
Human Factors and Regulatory Considerations
Vehicle lighting is fundamentally a safety tool; prioritizing clarity over flair. Best practices emphasize brief, intuitive cues: arrows, pulses, or expanding lights are universally understood, outperforming text or intricate symbols. Adherence to color and flash guidelines under standards like ECE in Europe or FMVSS in the U.S. is essential, covering red, amber, and white hues, duty cycles, and rates. Validation through user studies to assess recognition time, errors, and glance patterns in varied conditions, including daylight is necessary when developing ISD technology.
Recent 2025 studies underscore effective eHMI strategies for pedestrian interactions. Controlled experiments favor green, slow-rhythm flashes for yielding when pedestrian priority applies, and red, fast-rhythm flashes for vehicle precedence, with flashing enhancing perceived intent over steady lights (Figure 3). Symbols are preferred overall, but text like “Safe to Cross” or “Walk” paired with icons maximizes clarity when stopped. Text excels in message comprehension, while light bars enable faster detection and reaction, making a combined approach attractive in dynamic environments.
Fig 3. Pedestrian Study (Image © Driving Vision News (DVN), used with permission. Source: ‘Newsletter #921’, DVN, September 30 2025)
Regulations are adapting; for example, matrix adaptive driving beam (ADB) headlamps are now U.S. approved. Expressive ISD features are acceptable when they do not compromise the meaning of mandatory signals and remain within defined photometric and timing constraints. A smart strategy involves region-specific gating, enabling enhanced modes only where permitted and defaulting to a conventional baseline elsewhere.
The International Automotive Lighting and Light Signaling Expert Group (GTB) roadmap anticipates updates in a 2026 draft, alongside proposals for signaling projections and ADS status indicators.
Real-World ISD Examples
Intelligent Signal Displays are already moving from concept to reality. Opel’s Grandland AV2X demonstrator uses cyan lighting to indicate when its automated driving system is active, switches its signature to magenta with a warning symbol when a pedestrian is detected, and then shows a green walking figure once the vehicle has stopped and it is safe to cross, illustrating how color and animation can convey intent in real time (Figure 3).
In China, dedicated ADS lamps are beginning to scale in series production; DVN’s 2024 ISD study reports several hundred thousand vehicles already equipped, with strong penetration at BYD and growing adoption at brands such as Li Auto, Xiaomi, Xpeng, NIO, Zeekr, and Lynk. Meanwhile, vehicles like Human Horizons’ HiPhi X showcase fully programmable ISD panels that present interactive safety and status graphics at each corner of the car, underscoring that software-defined exterior signaling is entering a real, measurable deployment phase.
Designing the ISD System Architecture
Software plays a crucial role in an ISD system. An MCU-based controller runs a defined software program that maps vehicle states to approved lighting patterns, avoiding improvised behavior. Patterns are managed as versioned firmware, enabling testing, over-the-air updates, and adapted by region. Ensure deterministic synchronization between modules (for example a shared clock or time base on the bus) so animations stay aligned, avoid visible beating, and keep switching activity predictable for EMC tuning. Human-factors testing should then verify that the chosen patterns work in practice by measuring recognition time, error rate, and glance behavior in realistic traffic and lighting conditions.
To avoid visible flicker and camera banding, the pulse‑width modulation carrier frequency should stay above 20 to 32kHz. Use PWM dithering techniques, for example a 10+2-bit scheme, which consists of a 10-bit carrier at 156 kHz plus 2-bit frame dithering to yield an effective 12-bit dimming at 39kHz without dropping the fundamental PWM frequency. Implement PWM clock phase inversion, spread spectrum and staggered start times offset PWM phases across LED channels, to reduce electromagnetic interference peaks and meet CISPR-25 limits. Per‑channel current monitoring and fault protections improve uniformity and detect open or shorted LEDs, while ghost‑removal strategies minimize stray current artifacts in LED matrix arrays. Any thermal budgeting must account for worst‑case ambient conditions, enclosure heating, and animation duty cycles, allowing for derating when necessary to preserve brightness and operating lifespan. (Figure 4)
Fig 4. Factors which to consider in ISD design
Common pitfalls include vague icons or color choices, an excess of modes or animations that conflict with regulations, PWM frequencies that are low enough to cause visible flicker or camera banding, non‑deterministic timing between modules causing EMI spikes or visible beating, poor daytime legibility, and excessive thermal stress that forces premature derating.
Enabling LED Drivers
ISD modules rely on LED drivers that support high-frequency PWM, advanced dithering, phase control, robust diagnostics, and standard control interfaces such as I²C, SPI, UART, CAN, or serial-shift. Lumissil offers a broad portfolio of automotive-qualified AEC-Q100 and ASIL-B capable LED drivers designed for these requirements. For example, Lumissil’s IS32FL3776 matrix LED driver integrates all the critical functions for expressive, software-defined exterior lighting. With 36 constant-current channels configurable as a 36×6 matrix, it supports dense, individually addressable pixels ideal for rendering icons, animated turn signals, proximity-responsive bands, and ADS/ISD status indicators, all while minimizing bill-of-materials (BOM) complexity.
The device delivers high-bit PWM resolutions with selectable dithering modes to ensure smooth dimming transitions and precise control at low brightness levels. Built-in de-ghosting, low-headroom operation, and 8-bit LED channel current adjust (dot correction) work together to maintain visual uniformity and eliminate artifacts across the display surface. High-speed UART or SPI interfaces, combined with device addressing, enable synchronization of multiple modules within a single lamp assembly.
For EMC, the IS32FL3776 incorporates phase-delayed switching, spread-spectrum PWM clocking, and staged channel activation, features that significantly reduce power ripple and EMI emissions, ensuring compliance with CISPR-25 limits even during complex, high-duty-cycle animations.
For thermal management, the IS32FL3776 implements two methods: adaptive supply control and offloading current to external PMOS switches (Figure 5).
Fig 5. IS32FL3776 Matrix LED Driver for ISD
First, the device uses its internal 10-bit ADC to measure LED forward voltages and channel headroom, then computes the minimum supply voltage needed for the active matrix. This result is reported in the VOUT_MIN register and driven out on the FBO pin as a feedback signal to the external DC/DC converter. The DC/DC loop trims the LED supply rail down so that only a small headroom remains across the IS32FL3776 outputs, which directly reduces thermal dissipation proportional to V(headroom) × I(LED) × # of channels.
Second, in external MOS mode the six SW pins control six external P-channel MOSFETs, each supplying one matrix column. The IS32FL3776 controls these SW pins so that high-side conduction losses are shifted to the external FETs and PCB copper instead of the device’s QFN package. This combination of external PMOS column switching plus adaptive DC/DC control via FBO keeps the IC’s internal headroom and junction temperature low, which is especially important for high-pixel-density ISD lamps running complex animations.
From a reliability standpoint, the IS32FL3776 includes programmable diagnostics such as cycle-by-cycle LED open/short detection, ADC-based monitoring, over-current protection (OCP), under-voltage lockout (UVLO), and thermal shutdown. It is AEC-Q100 Grade 1 qualified to meet the stringent durability requirements for exterior automotive environments. Together, these features make it a compelling LED driver platform for scalable, standards-compliant, and visually distinctive intelligent signal displays.
Conclusion and Outlook
If lighting is becoming the language of vehicles, ISDs are the grammar that carries intent, identity, and trust. By integrating optics, matrix LED drivers, software, and human factors, engineering teams can create expressive yet safe signatures that redefine how vehicles communicate. Lumissil’s automotive-grade matrix and multi-channel LED drivers provide the high-frequency dithered PWM, thermal management, diagnostics, and scalability needed to implement these ISD concepts across automotive front, rear, and side lighting.
 
Contact Aaron Reynoso at areynoso@lumissil.com for any questions or comments.
Learn more about our products: www.lumissil.com
 

You must Register or Login to post a comment.

source