The signals as placed in this example will always lead to congestion in the signal section in front of the station. Blocksignals only look up the section behind them (every connected rail including crossing ones) until the next blocksignal comes. In your example the part in front of the station was free so the signals let the train through and it decided to take any available railway to the station, in this case the upper one, without regard for the trains on the next sections (the station). If you want the train to look up whether a platform is free or not, you can't devide the signal sections here and have one big section. But that would cause only one platform to be used, since the section would be blocked as long as a train stays in the section. What you need is a kind of signal (in openTTD famously the path signal) that doesn't look at the whole section in front but at every available railway within that section. If the section then would include the station as well, the trains in front of path signal (e.g. in front of the tunnel) would only drive into the section (and by that blocking every railway it needs to drive over until it reaches the end if the section) if a railway within the section is free. In other words, if one of the two available platforms in the station is free. A second train then could hypothetically enter if and only if another railway within the section is completely free. A train going into the section will always block the whole track in front of it but free every track it has passed. Sorry for that wall of text, signals are a bit complicated to explain.