yeah he is right. you will basicly need that second one to run a second engine ( unless they are running in the same train) the layout i made can run 2 trains, but I suppose only one at a time. still, you can just turn the block off, by setting the corresponding controller switch to the middle. just park your RDC or small commuter train on that long siding to bottom right when its not running. keep your locomotive on the yard track to keep it out of the way while the commuters are going home. you probably only need one power pack, but get 2 anyway. if you ever feel liek expanding your layout ( extending the track currently held by the commuter train to another place) you'll probably want to run more than one train at a time.