Wis. Stat. § 346.90: Following emergency vehicle.

The operator of any vehicle other than one on official business shall not follow an authorized emergency vehicle responding to a call or alarm closer than 500 feet or drive into or park his or her vehicle within the block where, or within 300 feet of the driveway entrance or similar point of access to a driveway or road on which, fire apparatus has stopped in response to an alarm. The personal vehicles of members of a volunteer fire department answering the alarm are considered on official business.