US 12/18 and County AB interchange

Project location | Project overview | Public involvement | Schedule | Traffic impacts/detours | Status/phase | Contact information

Project location

US 12/18 (Millpond Road to east of County AB), Madison - Dane County

Project overview

The purpose of the US 12/18 and County AB interchange project ​is to reduce the overall number and severity of crashes along the corridor, decrease travel time delays, expand bike/pedestrian access, and support community cohesion and economic development in the region.

Four components make up the need for the project:

  1. Safety
  2. Progress toward freeway conversion
  3. Accommodate local and regional growth
  4. Local connectivity and access

The Wisconsin Department of Transportation (WisDOT) has investigated numerous solutions to alleviate crashes and improve traffic operations along US 12/18 and recommends a grade-separated strategy. Federal Highway Safety Improvement Program (HSIP) funds have been committed to remove the two hazardous at-grade intersections at Millpond Road/ Long Drive and County AB.

A diamond interchange will be constructed just east of the existing County AB intersection with roundabouts at the ramp terminals. Access to US 12/18 will be eliminated at the Millpond Road/Long Drive intersection except for eastbound right turns. Frontage roads will be built to connect into the realigned County AB, allowing traffic from neighborhoods and businesses to gain access to US 12/18 through the interchange. Removal of these at-grade intersections will greatly increase safety, decrease delay, and support economic development through increased access.

The County AB interchange project is consistent with WisDOT’s plan for the corridor as a freeway facility and the city of Madison’s land use plan. Additionally, the proposed County AB interchange will provide improved pedestrian/bike access. Residents in neighborhoods to the north of US 12/18 will be able to safely cross the busy route on designated bike/pedestrian facilities.

WisDOT, the Ho-Chunk Nation, the city of Madison, and th​e town of Cottage Grove are partners on the recommended transportation solution.

Public involvement


  • Spring 2021  ​​Final Environmental Document
  • February 1, 2022 – Final Plans, Specifications and Estimate (PS&E)
  • Fall 2022 - Fall 2023 – Construction currently scheduled

Traffic impacts/detours

Traffic impacts are anticipated on US 12/18 during construction. These details will be discussed during the design phase.



Contact information

Derek Potter, P.E.
WisDOT Project Manager
(608) 246-3861

​John Fandrich
WisDOT Real Estate Specialist
(608) 245-5676

Steven Theisen
WisDOT Communications Manager
(608) 884-1230

Wisconsin Department of Transportation (WisDOT)
Southwest Region, Madison Office
2101 Wright Street
Madison, WI 53704
Phone: (608) 246-3800​
Fax: (608) 246-3843
TTY: 711

Project location | Project overview | Public involvement | Schedule | Traffic impacts/detours | Status/phase | Contact information