I don't know if this helps. It looks like you have track ends (buffers) beyond the trackmarks. What you need to know is that a track end is actually a signal that displays a permanent red (stop). If you have a siding with no track end, then the signals leading to that will not clear because they see it as "unsignalled track". Put the track end, and the preceding signal will clear to yellow, to allow the train to proceed at reduced speed towards the siding.
Now, I guess what you have happening is that the train approaches the track end, and stops behind the signal as it always would. But this means it stops short of the trackmark, so it cannot reach it. Hence the exclamation point on the driver's face. If you look at the notification area you will probably see a message something like "Driver XXXX waiting for track clearance".
You have a couple of options. One is to just move the trackmarks further away from the buffers (track ends), but this means you can't get the trains to stop nicely close to the buffers. Another is to extend the track then use some "Dummy Buffers". These are scenery items, and the train will actually drive right through them. My favourite solution though is very simple. Put an invisible signal between the trackmark and the track end. The invisible signal will display a yellow (caution) aspect, so the train will pass it if necessary to reach the trackmark. The train though will then approach the siding under a green light (because the signal before the siding will see the yellow invisible signal, not the red trackend). So be sure to have a suitably slow speed limit on the approach to the siding so you don't get the trains crashing into the buffers.
Look for Dummy Buffers or Invisible Signals on the DLS.
This one puzzled me somewhat when I first started building with Trainz.
Hope this helps
Regards
Chris
