Not sure if this would be any help to the devs when selecting AI trigger points, but in Britain we would aim to have at least 2 solid green aspects ahead of any approaching train. Similarly we aim to clear or 'pull-off' any train at a platform roughly 1 minute before booked departure time, the AI at present pulls-off at the exact departure time, which could actually end end delaying a train in the time it takes the brakes to release.