That of course stands for Every (Freakin) Numbered Highway in OHio
So first of all I highly recommend this website - Straight Line Diagrams (SLDs) from somewhere in ODOT I assume.
In any case my first pass was to check how many counties had to be visited. I found out that 80 of the 88 counties have numbered highways that are ONLY in that county. The 8 that do not are Allen, Auglaize, Fulton, Montgomery, Portage, Richland, Shelby, and Warren. So in theory I would not have to ever visit those counties.
I will keep you, my loyal non-readers, posted.