Lexus GS 350 Owner's Manual page 346

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
The Rear Cross Traffic Alert function is operational when
■
The BSM function is turned on.
●
The shift lever is in R.
●
Vehicle speed is less than approximately 8 km/h (5 mph).
●
Approaching vehicle speed is between approximately 8 km/h (5 mph) and 28 km/h
●
(18 mph).
GS350_300_GS F_OM_OM30J17E_(GE)
Fast 28 km/h (18 mph)
Slow 8 km/h (5 mph)
4-5. Using the driving support systems
1
Speed
345
Approximate
alert distance
20 m (65 ft.)
5.5 m (18 ft.)
4