FIFO. (First in first out)

[kiv@vftronic.no]

How is it possible to control «what train start first», I expected that software will give go access to train that enter a waiting position as number 1 prior then later arrived trains. In the movie the green train wait for a yellow train but also wait for a dark green that just entered wait track to continue up helix.
Any setups to control that in software?