I've noticed a few times that sometimes when crossing a river there is no road penalty, but this last game for the 1st time I noticed that I had an actual bridge graphic and no road penalty before engineering. Do these occur randomly purposefully or is this a bug?

edit: oops contstuction not engineering, please delete

the discovery of the tech construction allow to have bridges, and then to suffer no penalty when going through rivers.

As far as I know, it has been the case since vanilla 1.0 :)

/edit: read wrong, sorry.