All I'm getting from this is that Wikipedia is broken.
If you're going to say some article isn't "notable," then from where else are people going to get the information from? Even if it is an insignificant route in boondocky Wyoming, that insignificance shouldn't determine notability, but how the unique and reliable the information provided should, which is a pretty low threshold even if maps are what provide the information (and that's said as someone who doesn't consider maps totally reliable historical documents).
Notability is Wikipedia speak for
significance. It also means that someone else has
taken note of the topic to write about it. That other people have deemed it
noteworthy.
We've had two dueling standards at work to determine that concept an apply it in practice. Highway articles in general have worked under a Subject Notability Guideline called
WP:GEOROAD that says that highways with national- or state-/provincial-level designations are typically notable. Sadly, that word "typically" in there has started to cause trouble. There are other SNGs, but they're starting to be watered down from guidelines of their own to applications of the other method.
Most topics fall under the
General Notability Guideline (GNG), which says "A topic is presumed to be suitable for a stand-alone article or list when it has received significant coverage in reliable sources that are independent of the subject." A group of editors is strictly applying that guideline to all individual article topics. In short, Michigan's State Trunkline Highway System may easily meet GNG, but to them, that doesn't matter when deciding if an article on M-28 or M-212 should exist. If M-212 doesn't have "significant coverage" and if that coverage isn''t "independent of the subject", then they think that we shouldn't have an article on it. (Fortunately, M-212's status as the shortest signed state highway gets it some news articles.) So MDOT sources, strictly speaking, don't contribute to the assessment of notability, and yes, they're trying to discount inclusion on a map as contributing to notability.
Forking to a new Wiki saves all of the articles in their current states for now and allows them to be expanded and improved without this new deletion pressure. Perhaps the pendulum will swing back toward a more inclusionist view in the future.