Gasworks Siding Bridge, Bath
This seems to be the accepted name for a disused bridge across the River Avon, No. 203.
It connected the two sites on either side of the river belonging to the Bath Gas Works of the Bath Gas Light and Coke Company, following the connection of the gasworks with a siding from the Midland Railway in 1869. Initially railway wagons were drawn by horses, but in 1901 a locomotive was purchased.[1]
1870 'The loop line from the Gas Works to the Midland Railway is now complete, and was opened for traffic last week.'[2]
The two span plate girder bridge is surprisingly modern-looking for 1869, but in fact bridges of this type were first constructed about 20 years earlier. If this is the original bridge, it would have been made from wrought iron, which would explain the apparently limited amount of corrosion.
Latterly the bridge served only to carry steel gas pipes, presumably taking gas from the production plant to the gasholders.
The 2017 photos indicate that the girders were in remarkably good condition, with no evidence of perforation or oxide jacking such as might be expected on a badly-maintained steel bridge of that age.
The bridge was evidently modified at some point, being strengthened by bolting doubling plates onto the outside of the webs above the bottom flanges (photo 4). Also, the cross beams have been bolted to the doubled web plates, presumably having been moved from the now-redundant gussets (photo 5).
See here for a discussion on this and another nearby redundant bridge (Windsor Bridge, Bath).