Toyota PRUS V 2020 Owner's Manual page 237

Driving in vehicle-to-vehicle distance control mode
This mode employs a radar sensor to detect the presence of vehicles
up to approximately 100 m (328 ft.) ahead, determines the current
vehicle-to-vehicle following distance, and operates to maintain a suit-
able following distance from the vehicle ahead.
Note that vehicle-to-vehicle distance will close in when traveling on down-
hill slopes.
4-5. Using the driving support systems
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