I’m also a user who noticed that there is some issues with the signals or actually rather the pathfinding system of TF.
Let me give you two examples, the first being sort of a solution until something is changed in the game by the developers and the second showing why the current behavior will be a problem on more complex routes.
Example 1: You make an entry waiting line. The blue train is loading at platform A, the yellow trains are on the same line and for some reason has caught up with the blue train. To give the blue train clear path out of the station do a bit of double track before the station and put up one way signals as shown (the green dots). Note that none of the trains will use platform B even though the track layout actually permits it, in fact if there’s only one line to the station a single track station is enough. And as some users already pointed out the yellow trains in this example will be rather useless on the station since the blue train would have taken all or most of the passengers/cargo. The length and number of signal-blocks of the waiting track depends on the traffic load of your line.
Example 2: This shows the problem with the current behavior on a more complex layout. Let say you have 3 different lines all going to the same station and all the lines have different length. You’ll never be able to make sure you don’t end up in a situation where you’ll have one train waiting outside the station. In the best case scenario the lines will split evenly over the available tracks of the station as you make the lines. But let’s say in the current example line 1 and 2 both have selected track A and therefore the yellow train is waiting for track A to become free. Line 3 on the other hand has selected track B but since the yellow train is in the way the red train can’t access the station. The workaround would be a number of parallel waiting tracks outside the station and hope for the best or the same amount of tracks on the stations as there is lines and hope that the game splits the lines evenly over the number of tracks.
This shows there is quite a big weakness in the path finding system of TF. Actually as some earlier pointed out OpenTTD has a path finding system that works great. Also with the current behavior I would think it’s quite impossible to build an express train passing, meaning you have two one way tracks running parallel to make track number two a passing track for faster trains on the same line. Since the path finding system isn’t dynamic and the trains take the route available the express train would always end up waiting behind the slower train.
But simply, the path finding to a station can’t be locked to a certain track on that station, it has to be open for first available track at that station!