I am not sure what toyota has been doing. But my cars, my friends cars, and cars i've rented all had a switch to shut off traction.

The button is either labeled with the name of the system (ASC, DSC, TRAC, whatever) or a "danger" icon with an ! in a triangle; except in the mustang where the icon depicted a skidding wheel.

Also on almost all of the cars I have seen a light come on the dash when a wheel slips and traction control does something. There's an indication when the system is turned off, too, either a 'trac off' light, or the same light that indicates operation burns steady.

Some of the systems work a little differently. The first time I felt it in a GM car, all it did was kick the throttle pedal back up at me (you could feel it in your right foot!) Modern ones like yours are built into the ABS, and the brain watches all four wheel-speeds. Sometimes there is a secondary throttle valve ahead of the main throttle body, that will close on traction operation. There is a signal that goes to the ECU to request that the engine timing be retarded. The brake lights come on while traction is operating. I have heard of some more advanced systems that have a set of accelerometers and steering angle sensor.

If you could get it to do selective braking without interfering with throttle, this might be golden. Sadly almost nobody gives the driver this option!