SCL, here's a pdf from Illinois:
http://www.cyberdriveillinois.com/pu...dsd_cdl103.pdf
Look at page 3, 2/3 of the way down. They don't give explicit examples, but I think the rules are the same in Illinois as they are in WI. But it's possible that the police there (as in many other places) did not receive a proper education about these particular rules.