Interstate 40/85: What's Primary?

In the early 90's, Interstate 40 was added to Interstate 85 from Greensboro to Durham. Interstate 40 was now in one piece and not two pieces.

But, there's a problem. As seen in the first picture above, the Interstate 40 shields are before the Interstate 85 shields showing that Interstate 40 is the primary route. However, in the second picture, the exit numbers are Interstate 85 exit numbers. This causes a classic Road Conflict.

Here are the reasons why that Interstate 40 could be the primary: Interstate 40 is longer, older, 40 obviously comes before 85, more important, and connects some of the most important cities in North Carolina. In my opinion, that's primary.

Here are the reasons why that Interstate 85 could be the primary: Interstate 85 has been on the corridor longer and on the corridor first.

So make your pick. Mine is I-40, yours might be I-85. Their both good.