Toyota Prius 2019 Manual page 345

The Rear Cross Traffic Alert function detection areas
The areas that vehicles can be detected in are outlined below.
To give the driver a more consistent time to react, the buzzer can alert
for faster vehicles from farther away.
Example:
Approaching vehicle
Fast
Slow
■
The Rear Cross Traffic Alert function is operational when
●
The BSM system is set to on. (P. 149)
●
The shift position is in R.
●
Vehicle speed is less than approximately 5 mph (8 km/h).
● Approaching vehicle speed is between approximately 5 mph (8 km/h) and
18 mph (28 km/h).
PRIUS_OM_OM47C35U_(U)
4-5. Using the driving support systems
Speed
18 mph (28 km/h)
5 mph (8 km/h)
345
Approximate
1
alert distance
65 ft. (20 m)
18 ft. (5.5 m)
4