Acura Road Departure Mitigation (RDM) indicator

How to read it

Acura’s 2021 RDX manual says a camera behind the rearview mirror watches the white or yellow lane markings on each side. If the car gets too close to them without a turn signal on, RDM shows a Lane Departure message on the multi-information display, applies steering torque and vibrates the steering wheel rapidly. If its steering isn’t enough to keep the car on the road, it may apply braking, but only where the lane markings are solid continuous lines. The RDX’s system starts looking for lane markings between about 72 and 145 km/h (45 and 90 mph).

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When it comes on

The 2021 RDX and 2019 TLX manuals give the same reasons: a problem with RDM, or RDM shutting itself off while the temperature inside the camera is too high or the area around the camera is blocked by dirt or mud. On the RDX a blocked radar sensor turns it on too, and it may come on for a while in an enclosed space such as a tunnel, or when the Maximum Load Limit is exceeded. On the TLX it comes on for a few seconds when the power mode is set to ON, then goes off. On the 2025 MDX a problem with RDM turns on the amber Safety Support indicator.

What the manual says to do

For an indicator that stays on, the 2021 RDX and 2019 TLX manuals both say: “Stays on constantly - Have your vehicle checked by a dealer.”

Its three settings

The 2019 TLX manual says RDM can be set to Normal, Wide or Warning Only. Its message table gives two responses to the car drifting out of a detected lane: the steering wheel vibrating rapidly, or the wheel vibrating while the system also steers the car to help keep it in its lane.

What NHTSA calls it

NHTSA describes lane departure warning, which monitors the vehicle’s position in its lane and alerts the driver as it approaches or crosses lane markers, and lane keeping assistance, which automatically and gently steers to prevent the vehicle from leaving the lane. RDM does both. NHTSA adds that lane departure warning could prevent road departures and the crashes off the roadway that follow them. NHTSA notes that makers use different names for the same driver assistance technologies.