M-DOT Proposes Diverging Diamond Interchange for I-75 at 12 Mile Road

[Scottathew]

M-DOT is proposing a Diverging Diamond Interchange for I-75 at 12 Mile Road. This is the same kind of interchange that is currently at University Drive, Big Beaver Road, and 14 Mile Road. Keep in mind that the ones at Big Beaver and 14 Mile are a little messy and not in their final form yet.

DDI's eliminate many conflict points and opposing-traffic turns. This makes these intersections a lot safer than other designs.


Huge improvements over the previous design include the elimination of the tight loops to enter I-75. This means that traffic will no longer be entering I-75 at 12 Mile going 25 miles per hour with this new design. Much better for large trucks that have difficulty accelerating quickly.


Some folks might not like the change but I highly encourage folks to get familiar with them. These are a lot safer and as a father, husband, brother, and son I appreciate new road designs that keep my family safe.

[Gistok]

I see the logic in this design... but I bet old people will freak out a bit... like they do at roundabouts.

And here they were just getting used to the 26 Mile/M-53 Van Dyke Freeway interchange with roundabouts...

https://www.google.com/maps/@42.7133.../data=!3m1!1e3

[EGrant]

Merging onto 75 from 12 Mile is a harrowing experience. You need a sportscar just to get up to the speed of traffic in the short on ramps here. This would be a great idea.

[Wheels]

Constitution has already stared on this concept at 14mile and 16mile at I75.

[Honky Tonk]

Constitution has already stared on this concept at 14mile and 16mile at I75.

There will be amendments I'm sure.

[Hamtragedy]

Left on reds are legal on diverging diamonds unless stated otherwise.

And they are a piece of cake compared to a round-about. No comparison.

[royce]

Is the interchange at Telegraph and I-94 a DDI?

[ZenithCKLW]

Telegraph and 94 is a SPUI [[Single-point urban interchange). A SPUI is efficient with only one point requiring a traffic signal coordination, but there is still traffic crossing some opposing lanes.

[dtowncitylover]

Yes please! This is a frequent interchange for me and have always disliked it.

[townonenorth]

This will take some getting used to, although it seems easy enough. The traffic lights will be useful, I bet. Hopefully people don't back up into the other lanes as they are prone to do at rush hour.

[Scottathew]

Constitution has already stared on this concept at 14mile and 16mile at I75.

Typos aside, those DDI's are pretty much complete and functional. There's still a few things to be done and lane closures near them, so we don't have the full feel of how they'll actually function.

[hybridy]

Is that a park and ride I spy? What are plans for vacated land on southeast corner of the interchange?

[ZenithCKLW]

Has anyone experienced a DDI or SPUI when the traffic signals were out? Are they still easy enough to assume an all-way stop?

[Scottathew]

Has anyone experienced a DDI or SPUI when the traffic signals were out? Are they still easy enough to assume an all-way stop?

I have not. My assumption is that it wouldn't be too bad as it would need to be treated as a two-way stop, since traffic only comes from two directions. It might actually be far less confusing than a normal 4-way intersection.

[ZenithCKLW]

I just wonder about the traffic under the expressway between the two 2-way traffic lights. Can it clear fast enough through the stops so it doesn't back up into the previous 2-way intersection?

[5939DT]

I see the logic in this design... but I bet old people will freak out a bit... like they do at roundabouts.

Is 68 "old"?

I'm that old and don't mind roundabouts, 'course I have some experience driving in the UK and Ireland where these are common [[and they have some real doozies in and around London, lemme tellya).

[Gistok]

Is 68 "old"?

I'm that old and don't mind roundabouts, 'course I have some experience driving in the UK and Ireland where these are common [[and they have some real doozies in and around London, lemme tellya).

People who have driven in Britain/Ireland are exempt from any age criteria... I've been on the Motorways, ring roads, byways, and roundabouts of Oxfordshire myself.

[JBMcB]

Typos aside, those DDI's are pretty much complete and functional. There's still a few things to be done and lane closures near them, so we don't have the full feel of how they'll actually function.

I've driven through the 16 mile DDI several times during rush hour, and it seems to work pretty well so far. My concern is that there are several traffic lights immediately to either side, one for the city hall complex, and two for business parks. From what I understand, traffic needs to flow freely through the DDI to prevent long backups. It isn't an issue now, but as things reopen further and traffic volumes increase, it will be interesting to see if this has any effect.

Also, they need to put lane markers going into the DDI so people know where to go to get on the freeway. People are still stopping and trying to cut across lanes to get on the freeway at the last second.

[Scottathew]

MDOT Press Release:

MDOT receives federal approval to build innovative interchange at I-75 and 12 Mile Road

Fast facts:
- MDOT will proceed with building a diverging diamond interchange [DDI] at I-75 and 12 Mile Road in Oakland County.
- This innovative design will provide safety benefits for motorists and nonmotorized users.
- Rebuilding the interchange is expected to begin in late February 2022.

MADISON HEIGHTS, Mich. - The Michigan Department of Transportation [MDOT] will proceed with building a diverging diamond interchange [DDI] at I-75 and 12 Mile Road in Madison Heights. The decision to change to this innovative interchange design was approved by the Federal Highway Administration [FHWA] in late 2021. The interchange is part of the ongoing I-75 modernization project in Oakland County. DDIs were recently built at Big Beaver and 14 Mile roads along I-75, and the design is preferred by the Road Commission for Oakland County and the City of Madison Heights.

The existing 12 Mile Road interchange at I-75 is outdated with prevalent peak-hour congestion. The new interchange will be brought up to modern design standards and will improve capacity and safety by replacing loop ramps with elongated slips ramps, and will incorporate two-phase signals at the I-75 ramps that will minimize signal changes and reduce the potential for crashes. The DDI also will reduce the number of conflict points on 12 Mile Road for motorists looking to either access or leave the freeway, leading to further safety benefits for drivers and non-motorized users. More information about DDIs is available online.

The rebuilding of 12 Mile Road and the new interchange is expected to begin in late February. During the rebuilding phase, all ramps at the interchange will be closed and through-traffic on 12 Mile Road will be detoured between Stephenson Highway and Dartmouth Street. Access to businesses will be maintained on each side of the interchange.

Follow I-75 modernization progress on the web at www.Modernize75.com, or follow on Facebook at www.facebook.com/Modernize75 or on Twitter at www.twitter.com/Modernize75.

[Rocket]

Does this mean it will be very difficult / time consuming to get to the Home Depot and Lowe's?

I take that exit 2-3x a week to shop for work, and based on the diamond at 14 mile, I'm guessing you won't be able to turn left until you're almost at John R. ?

Perhaps you'll be able to turn into BJ's Wholesale? [GREAT name for a store by the way. Who knew?]

[kuuma]

Does this mean it will be very difficult / time consuming to get to the Home Depot and Lowe's

looks like Dartmouth St is still available to turn left to get to the home improvement stores.

14 mile looks good now, but took me a couple missed connections to get used to it. it all seems fine if cars are gonna stay the preferred solution, but i still think it's a missed opportunity to be doing all this momentous upgrading to 75 and not saving two lanes for rail.

[EGrant]

Man I hate merging onto 75 at that interchange. A much-needed update.