Is the second photo the bridge by the old Halberton station?
Certainly is! Served by the Tivvy Bumper, still to be found in Tiverton museum. There's a picture of the station in what passes as a heyday on
the Disused Stations website. Not an architectural marvel, really.
The first pic reminded me of Talbot Road bridge on the North Somerset, and the second looked like Whitchurch Halt (on the same line) to me - until I checked on Google Maps! Either the bridge has gone, or it's lost in the undergrowth!
https://goo.gl/maps/YPmiyqG95PKc6jSP9The third should have made it obvious that it weren't the North Som though...
There are similarities to the Whitchurch bridge, though not the Brislington one,
IMHO▸ . Having crossed the Whitchurch bridge many times, I can recall it being almost flush with the ground in the early 1980s, as though the field had risen to fill the gap. I would imagine that soil has been put there in large quantities.