If you use Garmin Basecamp for route planning you can choose what type of vehicle you want to plan your route for. If you use, say a motorcycle, it will plan your route using mostly 2-lane paved roads, and tend to avoid freeways. Then you upload that route to your GPS and you're off.
Changing the vehicle will change the way the route is mapped out. Bicycle will completely avoid interstates if at all possible, for instance.