US 23 north of Ann Arbor is one of Michigan's most congested and frustrating stretches' of freeway. The Michigan Department of Transportation has what it calls Flex Lanes and variable speed limits on that road. It seems few can agree or understand what the speed limit actually is.

This roadway has 2 or 3-ish lanes depending on time of day, traffic load or any number of other variables. The leftmost lane, which appears striped in yellow, is the flex lane that can be opened or closed.

When that lane is open, generally an 'advisory' speed is displayed. Say that speed is 10 miles per hour slower than the posted speed limit. Is that lower speed enforceable?

These questions came up on a popular road and travel group on Facebook. Notice the photo above, the flex lane is open and 60 mph is displayed overhead yet the posted speed limit to the right is 70 mph.

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The left flex lane is narrower than a standard freeway travel lane - it's basically allowing travel in a glorified shoulder. So should the lower speed limit apply only to that lane?

The official word from the Michigan Department of Transportation:

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The speed limit is 70 mph for the US-23 Flex Route. The speeds shown above the lanes are advisory speeds or “recommended” speeds based on areas of restricted sight distance when the shoulder is being used as a travel lane. The effectiveness of the advisory speed system is being reviewed and MDOT expects to make some improvements in this area over the next few years. However, it is still unknown whether the 60 mph advisory speed will remain in place whenever the shoulder is open to traffic.

The state is planning to extend the Flex Route concept further north on US 23 towards Flint and on I-96 through a portion of Oakland County.

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