Straight from Wisconsin DNR Rule book:
You may operate a snowmobile next to a roadway with due regard to
safety in the following manner:
_ Along U.S. numbered highways, state and county highways at
a distance of 10 or more feet from the roadway. Travel on the
median of a divided highway is prohibited except to cross.
_ Along town highways outside of the roadway. See the definition
of a town highway in the definitions.
_ During daylight hours, you may travel in either direction
regardless of the flow of vehicle traffic. _ At night, you must travel in the same direction as vehicle traffic
in the nearest lane unless the snowmobile trail is located at
least 40 feet from the roadway or the trail is separated from
the roadway by a head lamp barrier and the snowmobile trail
is approved by the DOT.
Other than a freeway, whenever it’s impractical to gain immediate
access to a snowmobile area next to the highway, you may operate
your snowmobile next to and parallel to the roadway for the purpose of
gaining access to and from the area of operation. Loading or unloading
your snowmobile must be done with due regard to safety at the
nearest practical point to the area of operation.
Snowmobiles traveling next to a roadway must observe roadway
speed limits or speed limits as posted.
Routes
You can ride on highways which have been designated as routes
and which are identified by signs. See the definition of a route in the
back of this booklet.
_ Towns, cities or villages may designate state trunk bridges,
a sidewalk or one lane of the bridge as a snowmobile route.
_ When a town, city or village designates a highway as snowmobile
route for snowmobile operation, you must observe the
following rules:
Snowmobiles must be operated on the extreme right
side of the roadway.
Left turns must be made as safely as possible from any
position depending on snow cover and other prevailing
conditions.
You must yield right-of-way to other vehicle traffic and
pedestrians.
If a town, city or village allows the “Purpose of Residential Access” or
the “Purpose of Access from Lodging” a snowmobile may be operated
on a portion of the roadway or shoulder of a highway, but only after
observing roadway speed limits. Check with your local officials to see if an ordinance exists before you ride.
Riding on roads illegally is the most common violation. Stick
to the trails and snowmobile routes.