* "Here's 2 shapes. Press the triangle."

* "Here's 2 numbers. Press the bigger one."

It would have to be something a trucker can easily solve at a glance, barely taking their eyes off the road. And they get a couple tries, a couple warnings, and then a loud siren and the event gets logged with their employer. 3 strikes system or something.

There's a dozen ways this could fail, but it's a fun thought experiment: "how do you determine a trucker is awake and functioning, without distracting them too much, annoying them too much, getting too many false positives, or putting electrodes on their brain?"