In the early 1830s, for roads, the pakset contains a timber bridge and its companion timber elevated roadway. It also contains a masonry bridge. But the companion elevated masonry roadway is missing in that era.
I believe the bridge and elevated roadway are meant to exist as a pair, become available at the same time.
The absence of the elevated roadway excludes the possibility of creating diagonal bridges. It also stops it being possible to make single tile bridge pieces, which can be very useful in conjunction with half height slopes*.
* this is useful because its presently not possible to create a tall bridge with half height approach ramps made of the bridge material , so one must make the more gentle ramps out of earth (a separate issue).
Thank you for noticing this. I do not think that there are any graphics for this (elevated roadways need diagonal graphics whereas bridges do not), and I have not produced bridge graphics before, so it might well be a considerable time before I am able to dedicate the time necessary to working on this (including learning how to produce bridge graphics).