Mazda 3 Owner's Manual page 218

In the following cases, the warnings may not activate even if your vehicle starts closing
in on the vehicle ahead.
You are driving at the same speed as the vehicle ahead.
Directly after the Mazda Radar Cruise Control (MRCC) system has been set.
When the accelerator pedal is depressed or directly after the accelerator pedal is
released.
Another vehicle cuts into the driving lane.
The following are not detected as physical objects.
Vehicles approaching in the opposite direction
Pedestrians
Stationary objects (stopped vehicles, obstructions)
If a vehicle ahead is traveling at an extremely low speed, the system may not detect it
correctly.
During headway control travel, do not set the system on two-wheeled vehicles such as
motorcycles and bicycles.
Do not use the Mazda Radar Cruise Control (MRCC) system under conditions in which
the close proximity warnings are frequently activated.
During headway control travel, the system accelerates and decelerates your vehicle in
conjunction with the speed of the vehicle ahead. However, if it is necessary to accelerate
for a lane change or if the vehicle ahead brakes suddenly causing you to close in on the
vehicle rapidly, accelerate using the accelerator pedal or decelerate using the brake
pedal depending on the conditions.
While the Mazda Radar Cruise Control (MRCC) system is in use, it does not cancel even
if the selector lever (automatic transaxle)/shift lever (manual transaxle) is operated and
any intended engine braking will not occur. If deceleration is required, lower the vehicle
speed setting or depress the brake pedal.
The brake lights are illuminated while the Mazda Radar Cruise Control (MRCC)
automatic braking is operating, however, they may not be illuminated while the vehicle is
on a down slope at the set vehicle speed or traveling at a constant speed and following a
vehicle ahead.
The Mazda Radar Cruise Control (MRCC) warning light (amber) fl ashes when the
system has a malfunction.
Refer to Warning Lights on page 4-22 .
Mazda Radar Cruise Control (MRCC)
When Driving
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