On the same tab as the tracks, is another tab at the top with track-objects. It looks like a red lantern where you will find signals, speed signs, switch-levers, and other nifty things.
Further to the right is direction markers, triggers, and track marks. At this point in the process, you can ignore the triggers for now. Direction markers are like one-way signs as they force the AI to take a track or avoid a track. Track marks can be named by clicking on the ? on the interface. A track mark is used when giving the AI driving instructions such as Drive via trackmark (Named south park east). The AI will then drive via track mark south park east and continue on its way to another track mark or destination.