TeeDee55 wrote:How are these determinations really being made?
While WME has "Major Highway", "Minor Highway", "Primary Street"; the terminology in Functional Classification (FC) is "(Other) Principal Arterial", "Minor Arterial", and "Major/Minor Collector". These FC types simply happen to translate to the WME types. It may not easily translate due to the continued display of the word "highway", but WME's Freeway/Major Highway/Minor Highway/Primary Street is the hierarchy that is still applicable for FC's Freeway/Principal Arterial/Minor Arterial/Collector.
With FC, appearances don't matter as much as what the function of the road entails. Things like speed limit, access points, number of lanes, and even numbered highway designation play less of a role than how the road factors into longer distance routing (as determined by MDOT). One of the goals in adopting this nationwide was to remove a lot of the subjectivity in determining road type, where an editor may classify something as a major highway due to [x], and then another editor would come along and change it to minor highway due to [y]. The roads then get flipped back and forth according to personal judgment. Instead, the decision is now in the hands of each state's department of transportation.
In this case, looking at Rochester Rd and Dequindre Rd on Oakland County's FC map, the red Principal Arterial designation is used for both even though the characters of the road are completely different, one is a state highway while the other is not, and so on. In classifying these as principals, someone at MDOT likely had to consider situations such as if I-75 did not exist, what would be the "best" or at least "most direct" route from Royal Oak to Rochester, or from Warren to Rochester. Traffic studies based on average annual daily traffic ("AADT") also come into play in determining classification. The character of two roads may be totally different, but appearances don't tell the whole story of the amount of traffic a road is handling or how it factors into longer distance routing from suburb to suburb.
In case you have not seen this, here is the thread for the national discussion. We had a similar one in the Michigan forum when it was decided that the state would serve as a test bed.