While progress on the single track T-TRAK modules has been at a grand halt for quite a while I have been working on other projects that include a small switching layout that uses T-TRAK technology, see it at:
Switching freight cars immediately implies coupling and uncoupling. I use MicroTrains couplers and they have a magnetic uncoupling system. The difficulty with it is that if permanent magnets are located permanently under the rails, you will have uncoupling when you want it to happen, but you can also have uncoupling happen when pulling a string of freight cars over the uncoupler and the train `jiggles’ in any sort of way. The solution is to have the permanent magnet below the rails only when you want it there. The following three YOUTUBE videos show my response to the situation. While I thought it out myself, probably I have seen something similar in the past and others of greater thought power and experience than myself have come to similar and/or better solutions.