KelleyCook wrote:Specifically I am talking about anything that is keyed as a Double-Red and Double-Grey (county-owned divided highways like Metro Parkway and Mound) on the Official State of Michigan Map -- http://tinyurl.com/MIstatemap
Note that looking over the map, I'm fairly confident that despite what the legend implies, the double grey line had an extra standard besides just the road being divided. Example Greenfield though it is divided through Dearborn didn't earn a double -- note it does not have Michigan Lefts nor is it designed for high speed. The entirety of Outer Drive though very wide also didn't qualify it as it is low speed and residential.
That's an interesting point. I've never paid attention to single versus double lines on the state map, but it must be more than just divided highway because there are a number of split roads in other parts of the state--and even within metro Detroit as you point out--that don't "earn" the double line. The presence of signed or even traffic-controlled Michigan Lefts does not seem to be a determining factor from what I can see though.
As sketch pointed out, we're using an "official" state map for functional classification of road types, but it's just not the same "official" map . As you point out with Long Lake and Evergreen, not all of the principal arterials are created equal in terms of what you typically think of as a "major" highway. Some roads that may not appear important still may carry 30,000+ vehicles per day on average though--even if they have a low speed limit or have fewer lanes. They serve an important function but have a meek appearance. Even if I don't necessarily agree with MDOT in all cases, putting the burden of the decision on them and having a consistent standard is worth it in my opinion.