I recently moved to China, and one detail on the road immediately caught my attention: the blue-turquoise lights appearing on some vehicles. That unusual signal sparked my curiosity and led me to look deeper into what it means, why it is being used, and whether it could become a useful standard for the future of driving.
The answer lies in one of the biggest challenges facing the automotive industry today. As vehicles become increasingly capable of driving themselves, one question remains surprisingly unresolved: how can a car communicate to the people around it that an automated driving system is currently in control?
A New Language on the Road
Modern driver assistance systems are progressing rapidly. According to the Society of Automotive Engineers (SAE) classification, a standard based on a 0-5 scale, developed to define vehicle automation levels1, Level 2 systems can control steering and speed simultaneously but still require constant driver supervision. Level 3 systems allow the driver to disengage under certain conditions. Level 4 systems can operate without human intervention within a defined operational area, while Level 5 would mean full automation in all conditions.
Yet, from the outside, most vehicles look exactly the same regardless of whether a human or an automated system is controlling them.
This creates an information gap. A cyclist approaching an intersection, a pedestrian crossing the street, or another driver merging into traffic has no way of knowing that the vehicle beside them is currently relying on automated systems.
Making that information visible could improve awareness and foster trust between vehicles and other road users.
This is where turquoise marker lights enter the conversation. By providing a clear visual signal that automation is engaged, they offer a simple and intuitive way for vehicles to communicate with the world around them. While still an emerging concept, this idea deserves broader adoption
Why Turquoise?
Mercedes-Benz has been leading efforts to standardize turquoise as the visual indicator of automated driving. The company first introduced its turquoise marker-light concept publicly in late 2023, when regulators in California and Nevada authorized the company to use the distinctive color to indicate that its Level 3 automated driving system was active.
Since then, the initiative has expanded to Germany, where Mercedes-Benz became the first manufacturer in Europe to receive approval for turquoise marker lights in March 2025. The German exemption is valid nationwide for testing purposes until July 2028. At the broader European level, no pan-European regulatory framework exists yet, but Germany's approval marks a significant first step toward one.
According to the company, the color was selected because it is clearly distinguishable from existing traffic signals, emergency lights, and conventional vehicle lighting.
Mercedes states that test studies showed turquoise performed better than other colors from both physiological and psychological perspectives. The color has also been incorporated into SAE Recommended Practice J3134 and Mercedes notes that it is part of broader regulatory discussions in China.
Unlike red, amber, or blue lights, turquoise is not already strongly associated with braking, turn signals, or emergency vehicles, reducing the risk of confusion.
Which Vehicles Could Benefit From it?
Today, most discussions around turquoise marker lights focus on Level 3 systems, such as Mercedes-Benz's DRIVE PILOT.
However, advanced Level 2 systems are already widespread. Volvo, Volkswagen, Tesla, BYD, Xiaomi and many other manufacturers offer systems capable of lane centering, adaptive cruise control and automated lane changes.
Although the driver remains responsible, these vehicles can perform significant portions of the driving task. Their behavior sometimes differs from that of a fully attentive human driver.
A visual signal indicating that automation assistance is active could help nearby road users better understand what they are interacting with.
Importantly, this would not mean that Level 2 vehicles are self-driving. Instead, it would simply acknowledge that some driving functions are currently being managed by software.
Some well-known examples include:
- Level 2: widely available across many brand in many countries, and infamously Tesla Full-Self Driving (which is not self-driving at all).
- Level 3: Mercedes-Benz (DRIVE PILOT), BMW (Personal Pilot L3).
- Level 4: Waymo and Baidu Apollo Go currently operate some of the world's largest commercial Level 4 services.
- Level 5: No Level 5 vehicle is commercially available today.
China Is Already Moving in That Direction
China has become one of the world's most dynamic markets for intelligent vehicles. In China, where I first noticed these lights, the idea feels especially practical: it is a visible way to make automation easier to understand for everyone outside the car.
As China continues to expand intelligent vehicle deployment, it is likely to play a major role in defining how automated vehicles communicate with their surroundings.
This is particularly significant because Chinese manufacturers are among the global leaders in advanced driver assistance technologies and are deploying these systems at scale.
Safety Through Transparency
It would be premature to claim that turquoise lights alone reduce accidents. There is currently no broad scientific consensus demonstrating a direct causal relationship.
However, transparency itself has value.
Road users continuously exchange information through brake lights, turn signals, hazard lights and eye contact. Automated driving removes some of these traditional cues.
External marker lights represent a logical evolution of that communication. They allow everyone around the vehicle to understand that software assistance is active and may influence the vehicle's behavior. This is especially relevant as many accidents involving Tesla vehicles have fueled public debate over who was actually driving, the human or the vehicle2.
Police officers, emergency responders and traffic authorities could immediately identify whether an automated driving mode is engaged.
A Small Change With Big Potential
The automotive industry standardized red brake lights, amber indicators and white reverse lights decades ago. Few people question their usefulness today.
Turquoise marker lights should become the next universal signal.
As automated driving expands from Level 2 assistance to Levels 3, 4 and eventually 5, vehicles should not remain silent about who, or what, is driving.
In Shanghai, I've come to appreciate their usefulness from the perspective of someone outside the vehicle. Whenever I notice one of these lights, I immediately know that the car may be relying on an automated driving system. It doesn't mean the vehicle is unsafe or that it will behave unpredictably, it simply reminds me to pay a little more attention. That extra awareness matters. Studies have shown that some drivers can become overly reliant on advanced driver assistance systems, potentially reducing their alertness compared with their baseline level of vigilance.
Giving cars a visible way to communicate with the outside world is not about replacing human responsibility. It is about increasing transparency.
And in road safety, better communication has always been a good place to start.
Sources
- Mercedes-Benz Group, « Approved to test special marker lights for automated driving » (2025): ~https://group.mercedes-benz.com/technology/autonomous-driving/driving/drive-pilot-marker-lights.html~
- Mercedes-Benz USA, DRIVE PILOT documentation: ~https://www.mbusa.com/en/drive-pilot~
- SAE J3134 (UNECE and China Compulsory Certification): ADS Marker Lamps (Recommended Practice).
- J3016 - Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles (April 2021)
- Mercedes Permitted to Use Turquoise Marker Lights for Drive Pilot (2023)
For an overview of the SAE Autonomous Driving levels, See Levels of Automation — NHTSA | National Highway Traffic Safety Administration ↩︎
Tesla's automated driving features, specifically Autopilot and Full Self-Driving (FSD), remain at the center of an intense public and regulatory safety debate. While federal regulators have launched multiple investigations into driver over-reliance and high-profile accidents, Tesla maintains that its technologies statistically reduce collision rates compared to purely human driving when properly supervised. ↩︎
