Toyota Prius Owner's Manual page 311

CAUTION

When the sensor may not be correctly detecting the vehicle ahead
Apply the brakes (or accelerator pedal) as necessary when any of the follow-
ing types of vehicles are in front of you.
As the sensor may not be able to correctly detect these types of vehicles,
the approach warning (P. 302) will not be activated, and a fatal or serious
accident may result.

Vehicles that cut in suddenly

Vehicles traveling at low speeds

Vehicles that are not moving

Vehicles with small rear ends (trailers with no load on board etc.)

Motorcycles traveling in the same lane

Vehicles splashing up water or snow

Conditions under which the vehicle-to-vehicle distance control may
not function correctly
Apply the brakes (or accelerator pedal) as necessary in the following condi-
tions as the radar sensor may not be able to correctly detect vehicles ahead,
and a fatal or serious accident may result:

When water or snow thrown up by the surrounding vehicles hinders the
functioning of the sensor

When your vehicle is pointing upwards (caused by a heavy load in the lug-
gage compartment etc.)

When the road curves or when the lanes are narrow

When steering wheel operation or your position in the lane is unstable

When the vehicle ahead of you decelerates suddenly
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