MDOT constructs divergent interchange at I-75 and 12 Mile in Madison Heights


Madison Heights, Mich. – Michigan’s Department of Transportation says it will advance plans to build an innovative transportation hub at a busy intersection in Madison Heights.

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MDOT will build a Diverging Diamond Interchange (DDI) at I-75 and 12 Mile Road after the design was approved by the Federal Highway Administration late last year.

The connection is part of the ongoing I-75 modernization project in Oakland County. DDIs were recently built at Big Beaver and 14 Mile streets along I-75, and the design is favored by the Road Commission for Oakland County and the city of Madison Heights.

Rebuilding of the 12 Mile Road and the new interchange is scheduled to begin in late February. During the conversion phase, all ramps at the interchange will be closed and through traffic will be diverted on the 12 Mile Road between Stephenson Highway and Dartmouth Street. Business access will be maintained on both sides of the interchange.


Related: The community is pushing for changes to the ‘dangerous junction’ in Birmingham

What exactly will the DDI look like and what are the benefits?

A DDI is SSimilar to a traditional diamond cross, most prevalent in the United States where the exit/entrance ramps form a diamond shape between the freeway and the country road. Right turns are treated the same at both a DDI and Diamond Interchange.

Different in the handling of left turns, because:

  • The intersections with the freeway ramps smoothly direct traffic on the surface road from the right side of the lane to the left side of the lane when the road intersects the freeway.

  • Traffic is on the left between the signals at the ramp crossings, all left turns are made at the entry/exit ramps without having to cross oncoming traffic.

  • Road geometry, signs and lane markings work together to make driving through the DDI very easy.

DDI blueprint. (MDOT)

Here’s a video showing how it works:

Security Benefits:

  • Reduces points of contention between vehicles and non-drivers by almost 50 percent.

  • Eliminates many of the worst accidents that happen at right angles.

  • Increases visibility for turning drivers.

  • Reduces the risk of people driving the wrong way on driveways.

  • Separates non-motorized users (bicycles and pedestrians) by guiding them through the median or along the sides of the lane.

  • Simplifies crosswalks and requires fewer lanes to cross at a time.

Operational Benefits

  • Offers a simple two-phase signal design with shorter cycle lengths (total time for the traffic signal to give the green light for ramp traffic and the green light for surface traffic).

  • Allows easy left and right turns from all directions.

  • Increases the number of vehicles turning left without requiring additional lanes.

  • There is more space between the signaled crossings at the ramps and one less signal.

Cost-efficient solution

  • Reduces construction costs compared to other forms of exchange.

  • Requires fewer lanes, therefore existing bridges and right-of-way can be used.

  • Uses a smaller project footprint, which means less impact on adjacent areas.

More: Oakland County news

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