The state is starting environmental studies for the project, the first step in a process that will require approval from the Federal Highway Administration and road improvements to get the stretch up to minimum Interstate standards.
If federal officials approve the change, the highway could become an interstate by 2015.
According to the Milwaukee Journal Sentinel, getting the road up to standards would cost $15 million to $20 million and would involve widening shoulders and installing cable guardrails along some medians.
The interstate route would primarily follow Highway 41's current path, but in Milwaukee would take an alternate route to avoid disrupting some neighborhoods, reported the Journal Sentinel. To do that, the new interstate would follow I-94 north from the Mitchell Interchange to I-894 west until it connected with Highway 45 and then the current Highway 41.
The state DOT has been working on the plans since 2005, when U.S. Rep. Tom Petri inserted language in a transportation bill designating the stretch as an interstate once federal requirements were met. The move is intended to attract more economic activity to the 142-mile corridor.