Lexus CT200h Owner's Manual page 600

5-2. Steps to take in an emergency

Warning message in radar cruise mode
In the following cases, the warning message may not be displayed even if
vehicle-to-vehicle distance decreases:

When your vehicle and the vehicle ahead are traveling at the same speed
or the vehicle ahead is traveling more quickly than your vehicle

When the vehicle ahead is traveling at a very low speed

Immediately after cruise control speed is set

At the instant the accelerator pedal is depressed
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