Generally roads like these will have disproportionately higher traffic just as long as there is something like a major supermarket or truck stop along it (especially adjacent to highways in rural areas), though functionally the roads remain the same, particularly since this is just one property driving up the traffic vs. a large transportation facility such as an airport or seaport.

An example of this I've noticed is the road leading up to the Buc-ee's in Florence, SC. Based on AADT alone, it could probably be a tertiary or secondary road, but it is functionally a dead-end street that has a bustling travel center located along it.

I think something like a Walmart could be a great case for bumping a road up from residential/unclassified to tertiary, granted it's not just a short little stub or dead-end road of some sort, but primary usually indicates the road is a more trans-regional highway like 14A or a major arterial like the business loop.