If you are like me, you might memorize routes somewhat like "left, left, right, left, left". Trying to decypher the beautiful in game map can be a bit stressful while shoveling coal or trying hard to not derail. This schematic depiction of the world map with all of its junctions and whether you can turn or not might help.
The Map of the World
The Map and How to Read It
Stations (depicted in yellow) are linked by thick black lines, the train tracks.
Every station has its name next to it as well as the services it provides as coloured circles.
See the possible turning directions below:
As you can see, 45 degree junctions can only be taken in the shallow direction, not the sharp one. In contrast, T-junctions can be taken in either direction.