Actuall reducing the loop to only 1 signal will fix it as Train Fever uses path signals. Please look at this diagram:
In the line on the bottom you can put 7 trains and they will never gridlock. It is demonstrated in video I gave link to at the top of page 3 in this thread.
Also please trust me a bit more. I may not have Train Fever yet but I played train games before and have solved my fair share of gridlock problems on my own a long time ago.