Simutrans Anleitung - How to build a two track section

When building to track sections between one track sections, it's best to do it as follows:

Insert two signals into the original one track section. Set the signals to the right direction. This can be done with the signal building tool.
After placing the signals build the second track.
Finally insert another two signals into the second track. Be sure to let them point in the opposite direction of the first two signals.