Lexus GS430 User Manual page 188

OCCUPANT RESTRAINT SYSTEMS
The SRS front airbags are designed to deploy in severe
(usually frontal) collisions where the magnitude and
duration of the forward deceleration of the vehicle
exceeds the designed threshold level.
The SRS front airbags will deploy if the severity of the impact
is above the designed threshold level, comparable to an
approximate 25 km/h (15 mph) collision in the U.S.A. and 30
km/h (18 mph) collision in Canada when the vehicle has the
impact straight into a fixed barrier that does not move or
deform.
However, this threshold velocity will be considerably higher if
the vehicle strikes an object, such as a parked vehicle or sign
pole, which can move or deform on impact, or if the vehicle is
involved in an underride collision (e.g. a collision in which the
front of the vehicle "underrides", or goes under, the bed of a
truck, etc.).
It is possible that in some collisions where the forward
deceleration of the vehicle is very close to the designed
threshold level, the SRS front airbags and the seat belt
pretensioners may not activate together.
Always wear your seat belts properly.
164
G16021
" 1 Collision from the side
2 Collision from the rear
3 Vehicle rollover
The SRS front airbags are not generally designed to inflate
if the vehicle is involved in a side or rear collision, if it rolls
over, or if it is involved in a low−speed frontal collision.
But, whenever a collision of any type causes sufficient
forward deceleration of the vehicle, deployment of the
SRS front airbags may occur.