Lexus 2003 LS Owner's Manual page 288

STARTING AND DRIVING
3 Resetting to a faster speed
Press the control lever upward in the "RES/ACC" 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/ACC" 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/COAST"
direction.
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4 Resetting to a slower speed
Press the control lever downward in the "SET/COAST"
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/COAST" 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/COAST" direction.
Even if you downshift the transmission from the "D" position to
"4" 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.