Elk Meadows Loop is a motorized (less than 50 inches) doubletrack that gives you access to many of the trails in the area. It also has a bunch of random single tracks come off of it that are fun to explore. I have not been able to find on official or unofficial maps.
Not only does the trail offer access to many trails in the area, it provides with some awesome scenery as you ride through you'll see pines, aspens, sage, wildflower, mountain views, and of course meadows. Wildlife is out and about, but the cows probably outnumber any big game animals.
The trail is fairly popular for atv's and has heavier traffic in the evening and on the weekends.