Lexus GS430 User Manual page 437

STARTING AND DRIVING
3 Resetting to a faster speed
Press the control lever upward in the "+ RES" direction and
hold it. Release the lever when the desired speed is attained.
While the lever is held upward, the vehicle will gradually gain
speed.
When the difference between the actual vehicle speed and the
set speed is less than 5 km/h (3 mph), the set speed can be
increased 1.6 km/h (1 mph) each time by pressing the control
lever upward in the "+ RES" direction quickly within 0.6
seconds.
A quicker way to reset the speed is to accelerate and then
press the control lever downward in the "– SET" direction.
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4 Resetting to a slower speed
Press the control lever downward in the "– SET" direction and
hold it. Release the lever when the desired speed is attained.
While the lever is held downward, the vehicle speed will
gradually decrease.
When the difference between the actual vehicle speed and the
set speed is less than 5 km/h (3 mph), the set speed can be
lowered 1.6 km/h (1 mph) each time by pressing the control
lever downward in the "– SET" direction quickly within 0.6
seconds.
A quicker way to reset the preset speed is to depress the brake
pedal and then press the control lever downward in the "– SET"
direction.
Even if you downshift the transmission from the "D" or "6" (sixth
range) to "5" (fifth range), or from "D" or "5" (fifth range) to "4"
(fourth range) in the conventional cruise control mode, engine
braking will not be applied because this mode is not cancelled.
To slow down, reset the cruise control to a slower speed with
the cruise control lever or depress the brake pedal. If you use
the brake pedal, cruise control is cancelled.