The command /swdr is used to relay the message from game chat to Dispatchers chat on SWDR - system that Dispatchers use to work with train traffic. If Your current scenery is Naterki (offline) and next would be for example Lublinek, Your command would look something like: /swdr Lublinek this is train 649337, is route from Naterki offline free to go? If the message is written correct it's in green colour and all Dispatchers will see the message, including Lublinek. He will send You the message also in green colour. If the route is approved You use selective call ZEW3 (F6) to initiate automatic dispatcher on scenery You're on to give You route and green signal.
If You have any pm or route changes on scenery the auto dispatcher won't be able to initiate. The only way out then is to spawn on next scenery and resume the tt from there or delete the tt and quit or start new somewhere else.