Wis. Stat. § 71.38
In this subchapter, "urban mass transportation of passengers" means the transportation of passengers by means of vehicles having a passenger-carrying capacity of 10 or more persons including the operator, such capacity to be determined by dividing by 20 the total seating space measured in inches, when such transportation takes place entirely within contiguous cities, villages or towns and in cities, villages or towns contiguous to that in which the carrier has its principal place of business, or within or between cities, villages or towns located within a radius of 10 miles of the city, village or town in which the carrier has its principal place of business, or entirely within one city, village or town contiguous thereto, or within a county having a population of 750,000 or more or within such county and the counties contiguous thereto, or suburban operations classified as such by the department of transportation.
Wis. Stat. § 71.38