If a high hill stood between A and B, it was important to decide whether the line should climb over it, pierce it with a tunnel, or make a detour to avoid it.
In other words, the merits, etc. of making detours are the consideration of the attitudes of the landowners whose property the line would cross, the convenience of other towns and villages, as well as connection with other railway lines.
We had to make a detour across a bridge down the river from here.