And the problem with the words is that they are accurate and do define the trail. That definition does not say a 49" vehicle can traverse the trail, it says a vehicle less than 50" is capable of traversing the trail. Most people read that and assume it means all trails meet the maximum width (50") which is not what it says nor is it what's on the ground. That 49" vehicle may be able to ride the trail; you may need a 40" vehicle. The only item on the map which tells you what may be better suited for the trail is the picture in the lower right, like I circled above. Just a bike, then the trail is best suited for a bike. Bike plus ATV means either is good to go on the trail. I've not found this system to be inaccurate or mis-leading if you know what it means to begin with.
As for what's on the triangle that's actually on the ground, I was just on parts of the Bull Gap system this past weekend and there were "ORV Trail" triangles with pictures of cycles on ORV Routes. There were also large signs on the Routes that said "Designated ORV Route".
Point is that you can't take what the triangle's picture indicates as proof of what the trail is for. Alas, this is a really bad example as that Route should be signed with ORV Route triangles period.