Wis. Stat. § 346.33: U-turns.

(1) The operator of a vehicle may not make a U-turn upon a highway at any of the following places:

(a) At any intersection at which traffic is being controlled by a traffic officer unless instructed by the officer to make a U-turn.

(b) In mid-block on any street in a business district, except where the highway is a divided highway and where the U-turn is made at an opening or crossover established by the authority in charge of the maintenance of the highway.

(c) In mid-block on any through highway in a residence district, except where the highway is a divided highway and where the U-turn is made at an opening or crossover established by the authority in charge of the maintenance of the highway.

(d) At any place where signs prohibiting a U-turn have been erected by the authority in charge of the maintenance of the highway.

(e) Upon a curve or upon the approach to or near the crest of a grade on any undivided highway where the vehicle cannot be seen by the driver of any other vehicle within 500 feet approaching from any direction.

(f) At any place where a U-turn cannot be made safely or without interfering with other traffic.

(1m) The operator of a vehicle shall exercise due care when making a U-turn upon a highway and shall only make a U-turn when the movement can be made safely and without interfering with other traffic.

(2) The operator of a vehicle may not back the vehicle at an intersection controlled by an official traffic control device for the purpose of making a U-turn.

(3) In this section, “mid-block” means any part of a street or highway other than an intersection.