signaling wye junctions

hey all,
how do i go about this
wye junction to a branch line of 66kms with one crossing loop

the top line is the mainline with a crossing loop to the right and a crossing loop to the left 25kms away
the signal to the left on the main line is a distant signal
problem is a1 will not procede pass crossing loop on branch line
if i drive it manulally past loop then tell a1 to drive to it will, back it wont
i can delete left branch of wye and problem solved
can't route based on real route
i know it's to do with block system, but the wye junction throws a spanner in the works cheers,
patchy

Simple answer is dont have any signals on the single track sections. Place signals on the loop lines just before the train enters the single line and place signals on the exit loop far enough along to allow a complete consist to clear the junction. Any signals oplaced on single track will almost allways end in conflict between two trains.