I run HO, 2-rail DC. By sequential operation, I mean that trains parked in a yard leave the yard, travel around the layout at least once and then return and stop where they began. As they re-enter their storage track, a reed switch connected to relays would cut power to the first track, apply power to the next track, and align turnouts as required for the next train to start.
I suspect there might be display layouts that use this type of operation and if I could talk to those folks that set it up I could save a lot of design time. Thanks, Ted