The rule comes from the 2021 infrastructure law, which instructed NHTSA to ensure every passenger vehicle can warn the driver of an imminent crash and automatically apply the brakes if the driver doesn’t react. NHTSA finalized the regulation in 2024, creating FMVSS 127, a performance-based standard that covers both vehicle-to-vehicle AEB and pedestrian AEB. Importantly, the rule is sensor-agnostic: it doesn’t tell manufacturers what technology to use, only what results the system must achieve. As long as the vehicle avoids the test obstacles under the defined conditions, manufacturers are free to choose any sensor or system design that meets the performance requirements.
To meet these performance requirements, AEB systems use a combination of sensors and software to detect hazards, assess the situation, and apply the brakes automatically. The system essentially performs the same “detect, decide, actuate” loop a human driver would, but in a fraction of the time.
To meet FMVSS 127 performance requirements, AEB systems use a combination of sensors and software to detect hazards, assess the situation, and apply the brakes automatically.
The system essentially performs the same “detect, decide, actuate” loop a human driver would, but in a fraction of the time.
Historically, many vehicles relied on a single mono camera AEB setup, but the new performance requirements are expected to push some manufacturers to add hardware, like secondary cameras or radar, to achieve consistent detection in more challenging conditions.
By combining multiple sensor inputs, the system can more confidently recognize obstacles and make braking decisions across a wider range of environments.
FMVSS 127 sets an ambitious but achievable benchmark for AEB systems, focusing on real performance rather than prescribing specific technologies.
By keeping the standard technology-neutral and evaluating the vehicle as a complete system, NHTSA encourages innovation across sensors, software, and control strategies. Although the requirements are demanding, from high-speed braking to consistent nighttime pedestrian detection, industry progress shows rapid improvement, giving manufacturers a clear target and enough lead time to refine their systems before 2029.
A central theme is balance. No single sensor or feature can meet every scenario, so robust AEB performance comes from layering complementary strengths. Cameras, radar, and optional LiDAR each contribute differently, while thermal infrared can address specific gaps like nighttime pedestrian detection. Likewise, advanced fusion and decision-making software tie these inputs together to create consistent, reliable behavior.
In the end, FMVSS 127 isn’t just about passing defined tests, it’s about driving system-level integration that elevates real-world safety. Automakers that combine high-quality sensing with intelligent software will not only meet the standard but deliver AEB systems capable of preventing collisions across the unpredictable conditions of everyday driving.
Discover how FMVSS 127 moves from rigorous test scenarios to proven safety in everyday driving.