It was a railroad, yet there's a hard curb along the gutter?
Yeah, I am not buying the railroad thing either. According to historical aerials, it was never anything other than a road. The bridge was being constructed in 1986 and was already a dirt road in 1990. In general, railroads don't get abandoned that fast. I will also say this is my opinion and I have never been to this area, not am I familiar with the history there.
What caught my attention is the near perfect arc coming off the west end of the bridge curling northwest and connecting to the Piney Creek Sub down along the creek below. That looks like an excavation cut almost the entire distance. Also, the width of that bridge deck is substandard even for roads back in the 1980s. It's interesting that today's GSV is drawing a road curling southwest off the bridge and zig-zagging towards the town below. I can't find any evidence of that one.
The Chessie System timetable (1980) shows the trackage on the Glade Creek and Raleigh sub connecting the "stations" of Blue Jay Junction, Glen Morgan and Beaver. And sure enough, this one checks out. Glen Morgan is down on Piney Creek below this bridge, so this "station" would have been close to where the bridge is today. If you rotate GSV away from the bridge, the backroad is a perfect railroad grade continuing as Mountain Edge Road and connecting tangent to CR-9/9 and later CR-9/8 (Orchard Hill Road) almost all the way into "downtown" Beaver. Add a thick Appalachian accent here
"We don't have many roads like that in West Virginia, if yoo know whut I mean". But I do wonder why the last half-mile of Orchard Hill Road veers away from the railroad grade.
Chances are good that the trackage was abandoned in place at the time that I-64 was being designed, so DOH probably designed the bridge to accommodate both either a track or road. West Virginia was reticent to cut off trackage access to big coal mines that might ever be able to reopen. About the only way to know for sure is to check whether the bridge was designed for railroad loads (including a layer of track ballast, crossties and rails on the deck).