The Subaru Ascent RAB system operates using four rear-mounted sonar sensors and provides two primary functions designed to assist the driver during reversing maneuvers.
- Sonar Audible Alarm function
This function continuously monitors the rear area of the Subaru Ascent and alerts the driver with warning messages on the center display and audible beeps when obstacles are detected.
- Automatic Braking function
If the Subaru Ascent determines that a collision risk is high, the system automatically reduces vehicle speed and applies braking force to help prevent impact or reduce the severity of the collision.

- When reversing
- When either strong automatic braking or torque control is applied to prevent collision (short or continuous warning beeps will sound)
- When the Subaru Ascent is brought to a complete stop by the system (continuous beep remains active)
- Detected obstacle (for example, a wall or barrier)
Detecting range

- Detection width: Approximately 6 in (15 cm) beyond each side of the Subaru Ascent
- Non-detectable zone: Approximately 20 in (50 cm) directly behind the rear bumper
- Detection length: Approximately 5 ft (1.5 m) from the rear of the Subaru Ascent
WARNING
If the Subaru Ascent becomes trapped at a railroad crossing and you attempt to reverse through the barrier, the system may detect the gate as an obstacle and automatically apply the brakes. In such a situation, remain calm and either continue pressing the accelerator pedal or manually cancel the RAB system. Refer to "Canceling the Reverse Automatic Braking (RAB) system operation" for instructions.
The Subaru Ascent Reverse Automatic Braking system significantly enhances safety during reversing by assisting with obstacle detection and emergency braking. However, it should always be used as a supplementary feature, with the driver maintaining full awareness and control of the vehicle at all times.
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