Yep - I totally agree, although I'm not sure which classification (primary/secondary) is more merited here. Essentially, I went through all of ND's major highways and reclassified them based on NDDOT's classifications, marking "State Corridor" highways as primary and "District Corridor" and "District Collector" highways as secondary with a few exceptions (e.g. setting ND 10 to tertiary). This did unfortunately yield numerous inconsistencies across state/province lines that I was unsure how to handle, especially since neighboring state/province DOT classification schemes appears to differ from NDDOT's.