MountainBiking is a non-motorized activity!

The US Forest Service has officially clarified that mountain biking is a non-motorized activity, and has included this description in the Forest Service Handbook and Manual—a move that could pave the way for mountain bikers to gain the same rights to some trails as those enjoyed by hikers and equestrians. This action is the much-anticipated follow-up to the internal memo distributed at an IMBA summit last June by Jim Bedwell, the Forest Service Director for Recreation, Heritage and Volunteers. The memo initially clarified the nature of mountain biking as “a non-motorized use of the National Forest Systems trail, along with hiking and horseback riding.”
When this initial announcement was made, Bedwell explained that letters such as the memo are often a prelude to official policy revisions, but he cautioned that they do not constitute “official” precedent.
...."bicycling is “a potentially suitable use on all trail classes,” and that “the environmental impacts of bicycling are similar to hiking and less than other uses."