You need to put additional signals along the line. If the signals are too far apart, the AI will travel at halfspeed like they're running on yellow signals.
A trigger, which I haven't played with yet, allows additional functions to happen that are 'triggered' by a trains action. Let's say for example, you need to have a shunter come out and pick-up a goods train once the road freight arrives. You'd place a trigger on the mainline, or yard lead, that is triggered by the freight train. The trigger is programmed through a script to notify the shunter that your freight has arrived, and is ready for pick-up.
Hope this explains this. I'm sure the other more experienced users can help more with this.
John
