Can bridges be listed in the way buildings are? I suspect a case could
be made that the modification is necessary for the function of the
structure, given the dammage caused to it by excessive modern traffic.

Robin

Yes they can be listed and are indeed so. For example, Battersea Bridge
is listed grade II, as are several other Thames Bridges. Exactly the
same rules apply to listed bridges as other listed buildings, including
the ability to alter them with permission. In the case of Battersea
Bridge, it was possible to modify the structure at the time of the
extensive refurbishment and strengthening a few years ago by installing
Trief kerbs, albeit in a granite finish, to keep vehicles from straying
onto the footways which were not capable of carrying their weight and
the cast iron parapets could not have restrained a vehicle from going
over the edge. The result altered the appearance of the bridge, but
that was better than the alternative of replacing the parapets with
modern, stronger ones that could not be designed to an appropriate
scale or style.

At the same time, the 1960's street lighting was replaced with modern
versions in the style of the original Victorian columns. All of this
required the agreement of English Heritage who were very cooperative.

Peter