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About the I-41 Project

Explore the Selected Project Improvements

Before the I-41 Project was approved for construction, WisDOT developed and studied multiple alternatives to reduce congestion, and update the roadway and bridges to meet current design standards.

WisDOT factored feedback from the public, tribes, businesses, agencies and local governments during the evaluation, which assessed each alternative’s ability to address the project’s purpose and need, and its potential environmental impacts, required right of way, and estimated cost.

Hover over the icons to see detailed information!

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WIS 15/County OO (Northland Avenue) Interchange

Diverging Diamond Interchange


This interchange will be reconstructed as a diverging diamond interchange to better accommodate higher volumes of traffic more safely. The merge distance for the I-41 northbound entrance ramp will also be increased.

WIS 441 System Interchange 

55 mph Flyover Ramp


The 55 mph flyover ramp alternative requires less land, has fewer impacts and costs less than a 60 mph flyover alternative while offering similar operational and safety benefits.

County S (Freedom Road) Interchange

Diamond Interchange with Roundabouts


This interchange will be reconstructed to diamond interchange with roundabouts at the County S/Mid Valley Drive and County S/French Road intersections.

Southbridge Interchange *NEW 

Diamond Interchange with Roundabouts


WisDOT will construct a new diamond interchange with multi-lane roundabouts.
A shared use path will also be added on the north side of Southbridge Road.

Please visit the link
below to learn more: Brown County South Bridge Project

Auxiliary Lanes

An auxiliary lane is an extra lane added between interchange on- and off-ramps. It is used to ease speed changes, balance the traffic load, and provide an efficient way to weave into and out of traffic while lessening congestion in the through lanes.

View Animation

Locations (5):

From WIS 96 to WIS 15
From WIS 47 to County E
WIS 441 from I-41 to County OO

From WIS 55 to County J
From Southbridge Road Interchange to County F

Auxiliary lanes will be built between these closely spaced interchanges in addition to a third travel lane that will be built as part of the I-41 Mainline improvements.

Collector-Distributor Road

Location (1):

From County E to WIS 441

A collector-distributor or C-D road will improve safety, requires less land and is less expensive than the alternatively considered braided ramp option, while providing a safe connection with acceptable traffic operations.

Visualizing the Improvements

Do you know the difference between an auxiliary lane and a collector-distributor road? How about the different types of diamond interchanges?

The I-41 Project will add innovative roadway and interchange designs to enhance safety and traffic operations.

The animations below show six designs the reconstructed project area will include.

An auxiliary lane is an extra lane added between interchange on- and off-ramps. It is used for speed changes and the maneuvering of entering and exiting traffic. It provides an efficient way to weave into and out of traffic while lessening congestion in the through lanes. Auxiliary lanes balance the traffic load and maintain a more uniform level of service on the highway.
A collector-distributor (C-D) road runs parallel to the main travel lanes of a highway and connects it to frontage roads or ramps. C-D roads are found at closely spaced interchanges to separate the congestion caused by merging and diverging ramp traffic from the through highway traffic.
A modern roundabout is a circular intersection in which drivers travel counterclockwise around a center island. Drivers yield to traffic already in the roundabout, then enter the circular roadway and exit at the desired street. To go straight or turn right, drivers use the outer lane(s); to go straight or turn left, drivers use the inner lane(s).
A diamond interchange with signals features two, closely spaced signalized intersections at the crossing of a ramp terminal and side street. The interchange includes four ramps – two exiting and two entering the free-flow highway. Diamond interchange designs are very economical compared with other options because they require less land and materials to construct.
A diverging diamond interchange is an innovative design used to connect a freeway (like I-41) and a major roadway. Within the interchange, traffic on the major roadway briefly drives on the left side of the road to allow left-turn movements without crossing oncoming traffic or stopping. A diverging diamond interchange has fewer conflict points, reducing the risk of crashes, and has greater capacity for vehicles.
A diamond interchange with roundabouts (also called a double roundabout interchange) is similar to a diverging diamond interchange in that traffic briefly drives on the left side of the road to allow for more efficient left-turn movements; however, by having roundabouts instead of signalized intersections, the design helps avoid backups onto the freeway in areas with high traffic flow.
The higher the driving speed, the farther drivers need to see obstructions.

Get to Know Your Project

WisDOT is committed to enhancing the accessibility and public understanding of the planning, design and construction of its projects.

Our project team uses social media platforms to share information about various tasks involved in reconstructing I-41 that are not as visible as the orange barrels we see in construction zones.

For frequently asked questions, visit our FAQs.

Follow us on Facebook and X (formerly Twitter) for these behind-the-scenes updates.

GOBBLE GOBBLE GOT CAR TROUBLE? WisDOT Safety Patrol basic services: Relocate disabled vehicles, Provide small amounts of fuel, Handle minor repairs Change flat tires Jump-start batteries, Remove small non-hazardous debris from the roadway, Assist with traffic control and crash scene clearance.
Connecting Streams WisDOT - WisDOT is installing bridges and culverts to allow the natural flow of streams in 28 different crossings.
What's happening on I-41? Working With the DNR - WisDOT and the DNR work together to ensure that the I-41 project considers: public lands and trails. water ways. wetlands. erosion control. threatened and endangered species. stormwater management. invasive species. habitat connectivity.
The higher the driving speed, the farther drivers need to see obstructions.
WisDOT plans for maximum visibility to allow drivers to see objects on and off the road. Factors that affect sight distance include buildings, weather, pedestrians, foliage and animals.
The 1-41 Project is using traffic count information to improve the safety and design of the roadway. More than 50,000 vehicles on average use the project corridor every day.
Did you know that Wisconsin has over 26,000 traffic count locations? To count traffic, WisDOT uses pole-mounted traffic cameras that record video footage, and induction loops, which are insulated wire strips that lie across the road with magnetic fields that sense vehicles as they drive over the strip.
The I-41 Project is in the design phase, which will include work related to design plans, specifications and engineering estimates.
Professional surveyors are taking measurements along the I-41 Project corridor.
What markers do we use to make measurements? Man made features, natural features and property boundaries.
Geotechnical investigations willbe taking place along I-41 as part of the reconstruction project. You might see and hear drill rigs as you travel through the project corridor.
In a Geotechnical investigation, soil samples will be taken and the data will be used by engineers when designing roads, bridges and other structures.
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