Reservation Ridge is a collection of ATV trails that is overseen by the Ashley National Forest. As with all National Forest managed lands they do require that you be licensed and wear a DOT approved helmet when riding your ATV on their lands as well as have a spark arrestor and muffler installed on your ATV to cut down on the chance of forest fires as well as the noise that ATVs can put out.
The Reservation Ridge ATV trail runs southwest along the border of the forest and is a scenic and fun ride on your ATV. The trailhead for riding your ATV at Reservation Ridge is not listed on any map, however that the Uinta National Forest permits ATV travel along FR 081. Presumably, somewhere in this section of road there is a location where you may find a place appropriate to pull off and unload your machines and enter the ATV trail.
You will find nearly 12 entrances to the Ashley National Forest on the southwest side that are open to ATV travel. The majority of these ATV trails are barely 2-miles each. If you want a longer ATV ride check out route FR 066 which meets with FR 148 and loops back along FR 149.
There is only one forest road that extends westward from the ridge aside from FR 081, the one you would have come up, it is FR 119. This part of the ATV trail has several spurs to the north and south making this an interesting area to check out during your ATV ride.
Make sure and follow the standards put forth by Treadlightly and leave no trace of your ATV ride. This helps preserve the trails for future generations of ATV riders.