Toyota PRIUS 2014 Manual page 38

1-1. Plug-in hybrid system
Charging (P. 84)
Vehicle proximity notification system
When driving with the gasoline engine stopped, a sound, which
changes in accordance with the driving speed, will be played in order
to warn people nearby of the vehicle's approach. The sound will stop
when the vehicle speed exceeds approximately 15 mph (25 km/h).
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PRIUS PHV_OM_OM47856U_(U)
In order to drive in EV mode,
charge the hybrid battery (trac-
tion battery) from an external
power source before using your
vehicle.
If there is not enough charge
remaining in the hybrid battery
(traction battery), it is possible
that the vehicle cannot be driven
in EV mode or the distance that
can be driven in EV mode will
become shorter.