Modular building of tall wood trestles

I think of module construction of bridges and buildings as a recent technology development. But this photo shows how it could be done for tall trestle bridges.

Allan C Wirkkala posted
Cable work. They did much with very limited equipment.
[This allows them to build the bents with the safety of being closer to the ground. I'm trying to figure out if it also allows some of the bents to be built in parallel, thus reducing the construction interval.]

The construction photos I have seen used a travelling derrick to "stick build" the trestle. I found some examples of that technique.

TheVintageNews
[We can see the base of the boom of the travelling derrick at the top of the photo.]

TheVintageNews
[It is not clear to me how they raised the timbers up into position for this trestle.]

AlaskaRailroad

AlaskaRailroad
[Replacing or adding timbers would have to be done as "stick work."]