Ride across the USA

[Lord Popgun]

In Virginia, the annual state inspection for vehicles says: Measure in two adjacent tread grooves where tread is thinnest. If either of the grooves measure 2/32 of an inch or more, no further measurements are necessary and tread depth is satisfactory. Do not take measurements from the tread wear indicators.

6. If both adjacent grooves measure less than 2/32 of an inch, the tire tread depth must be measured again at two additional equally spaced intervals around the circumference of the tire in a like manner as the first measurement. Refer to Figure 1. If the tread depth is less than 2/32 of an inch in two adjacent tread grooves at each of the equally spaced intervals, the tire must be rejected.
MEASURE WHERE THE TREAD IS THINNEST IN TWO ADJACENT TREAD GROOVES

It also says if the tread wear indicators are in contact with the ground the inspection fails, or if showing fabric or steel belts, etc.