All of the signals are one-way in that picture. Using this exact setup, you're good even if you use one-way path signals only (the rightmost one on the signal GUI). One-way signals only allow trains to pass in one direction. As we have 2 tracks in this setup, one towards the mine and one towards the power station, it's expected that the trains will only go one way on their respective tracks.
And yes, if there is a train loading at the station, and a second train arrives, it will choose the other platform and start loading there. If a third train arrives, it will wait at the signal until one of the trains leaves the station.
Remember, trains can only crash in one of these situations:
- You explicitly tell a train to ignore a red signal. Only do this if you know what you're doing.
- You are doing construction work while there are trains running on the tracks. This includes modifying/removing signals while your trains are there.
So as long as you don't do any of these things, your trains won't crash. The worst thing that can happen is that they wait indefinitely in the depot or at some signals because the path is not clear.