Lexus 2003 LS Owner's Manual page 272

STARTING AND DRIVING
31L159
Dynamic laser cruise control should not be used in
circumstances which are inappropriate for any cruise control
such as entering freeway on–ramps or off–ramps.
CAUTION
The dynamic laser cruise control should not be used
when exiting from, or when entering or merging onto a
freeway. When you are following a slower moving
vehicle and exiting, the sensor does not detect the
vehicle and will accelerate to preset speed.
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Turning on the system
31L175a
To operate the dynamic laser cruise control, push the main
switch. This turns the system on. When the "CRUISE"
indicator light in the instrument cluster comes on and "RADAR
READY" appears on the multi–information display, you can
now set your desired cruising speed and vehicle–to–vehicle
distance. Pushing the main switch again will turn the system
completely off and "CRUISE OFF" will appear in the
multi–information display.
When the ignition is turned off, the main switch is also
automatically turned off. To use the dynamic laser cruise
control again, push the main switch again to turn it on.
When the ignition is turned off, all the preset data is cleared.
When you use the dynamic laser cruise control again, you
need to reset the data.