Wis. Stat. § 343.75: Control group testing by department.

The department may exempt certain persons from one or more of the mandatory requirements of this chapter to establish a test group in order to compare this group with a group of persons not exempted from any of the mandatory requirements of this chapter. After comparing these 2 groups, the department shall determine what effect, if any, that a particular mandatory requirement may have on highway safety in this state. The department shall submit any findings in this regard to the secretary who shall include them in the report required under s. 15.04 (1) (d).