Toyota Prius 2011 Manual page 226

2-4. Using other driving systems
Example of constant speed cruising
When there are no vehicles ahead
The vehicle travels at the speed set by the driver. The desired vehicle-to-
vehicle distance can also be set by operating the vehicle-to-vehicle dis-
tance control.
Example of deceleration cruising
When the vehicle ahead is driving slower than the set speed
When a vehicle is detected running ahead of you, the system automati-
cally decelerates your vehicle. When a greater reduction in vehicle speed
is necessary, the system applies the brakes. A warning tone warns you
when the system cannot decelerate sufficiently to prevent your vehicle
from closing in on the vehicle ahead.
Example of follow-up cruising 
When following a vehicle driving slower than the set speed
The system continues follow-up cruising while adjusting for changes in the
speed of the vehicle ahead in order to maintain the vehicle-to-vehicle dis-
tance set by the driver.
Example of acceleration 
When there are no longer any vehicles ahead driving slower than
the set speed
The system accelerates until the set speed is reached. The system then
returns to constant speed cruising.
Approach warning
When your vehicle is too close to a vehicle ahead, and sufficient
automatic deceleration via the cruise control is not possible, the dis-
play will flash and the buzzer will sound to alert the driver. An exam-
ple of this would be if another driver cuts in front of you while you are
following a vehicle. Apply the brakes to ensure an appropriate vehi-
cle-to-vehicle distance.
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