I am looking for a word, or multiple words, which would fit between the terms 'minor' and 'major'. For example: 'Major arterial road' and 'minor arterial road' describe two types of roads with particular traffic flows (and design requirements), but what if there is a scenario which does not fit any of the two precisely, but sits somewhere in between?
The reason I am asking is that I am attempting to devise a naming convention for drawing layers in CAD. Usually a 'minor' and a 'major' layer suffice. An example would be lines depicting concrete, where the 'major' lines are the outlines and edges and the 'minor' lines interior corners and hidden lines. Now I have come across a few scenarios where I need another option in between.
Please note that I am not asking for help with creating a naming convention. I am looking for a word in the English Language that is between 'minor' and 'major'.