When the drug testing first started in Illinois, I had an employee, and enrolled him in the program.  I was told I had to be in the program as well, as I was also a driver.

The drug testing involved surprise tests, they told the employer when they would be there so the driver was present when the person doing the testing arrived.  I was not to tell the driver he was to be tested, it was to be a surprise.

I was also told I would be subject to random testing, I would be told as an employer when it would happen, but I was not to tell myself that I would be tested at that time.

After a few years of that silliness, they exempted employer drivers from drug testing in Illinois, but my employee was tested at least once a year.

Yes, the above is a true story, silly as it sounds.

EDIT:  I never hauled grain for hire, just my own grain.  I was still under the same rules as someone who hauled for hire.  My farm plates were not legal for hire trucking.