Modern Vehicle Sensors Under FMVSS 127

Modern AEB systems rely on a combination of cameras, radar, and increasingly LiDAR, each contributing different strengths.

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How Cameras, Radar, and LiDAR Support AEB

Cameras

Cameras provide detailed visual cues for identifying vehicles, pedestrians, and lane features.

Radar

Radar offers reliable distance and speed measurement and performs well in rain, fog, and darkness.

LiDAR

LiDAR, used in some higher-end systems, adds precise 3D mapping and helps distinguish objects with greater spatial accuracy. While powerful, LiDAR remains costly, and NHTSA notes it is not required for FMVSS 127 compliance

A Common Challenge Across Vehicle Sensors

Even with these sensors, there is a shared challenge: performance drops in low-light and low-contrast situations. Cameras depend on illumination, radar cannot resolve human shape, and LiDAR reflects off surfaces rather than detecting heat. Nighttime pedestrian recognition, one of FMVSS 127’s toughest requirements, exposes this gap clearly.

The Strength of Infrared Sensing

Infrared (thermal) sensing strengthens the overall sensor system.

Thermal cameras detect heat signatures instead of relying on visible light, making pedestrians and animals stand out even when the environment is dark, cluttered, or visually low contrast. They maintain stable detection in conditions that degrade standard sensors, such as nighttime, glare, fog, and complex backgrounds. Several manufacturers have pointed out that infrared may be necessary to consistently meet the most demanding nighttime pedestrian tests in the new standard.

Vehicle Sensor Capabilities and Constraints

Sensor Type Advantages (FMVSS 127 Context) Limitations / Challenges
Camera (Visible-light)
  • Low cost and widely deployed as the primary sensor in many AEB systems.
  • Able to identify and classify pedestrians, vehicles, and road features based on appearance
  • Strong support from existing OEM software stacks and ADAS architectures
  • Strongly dependent on lighting , performance drops at night, in glare, or low-contrast scenes.
  • Easily obstructed by rain, mud, snow, or debris, which is why FMVSS 127 requires systems to detect and warn when cameras are impaired.
  • Headlight illumination limits how far ahead pedestrians can be reliably detected at speed.
Radar
  • Provides accurate distance and relative speed
  • Helps stabilize detection performance in high-speed scenarios where timing margins for AEB activation are tight.
  • Often paired with cameras to meet stricter detection and timing requirements.
  • Higher cost than cameras.
  • NHTSA did not mandate radar, as camera-based systems can meet the standard if sufficiently capable.
LiDAR
  • High-resolution 3D sensing improves shape, edge, and position accuracy, useful for smaller or low-contrast objects.
  • Performs consistently regardless of ambient lighting.
  • Much higher cost compared to cameras or radar.
  • NHTSA’s analysis determined LiDAR is not required to meet FMVSS 127, compliance can be achieved using more common sensors.
  • Integration, cleaning, and packaging challenges in mass-market vehicles.
Infrared (Thermal) Camera
  • Detects heat signatures, providing true night vision, strong performance in darkness, glare, fog, or when visible-light cameras lose contrast.
  • Enhances pedestrian detection regardless of clothing color or background lighting.
  • Offers complementary information to visible cameras, improving continuity of pedestrian tracking in challenging scenes.
  • Not yet common in production ADAS
  • Typically used as a supplemental sensor
  • The standard does not require IR