Gm11

Just wanted to add a couple of points, a linear Hall sensor would allow you to detect range upto around 11 inches each way (depending), you shouldnt need magnets as most hall sensors if used correctly will pick up the motor flux easy enough. Also IR smd diodes and transistors can be used as a kind of bar code reader, the idea is simple enough, you put a tiny 2x2mm smd IR led and smd IR transistor next to each other, then print 'stickers' on any printer with barcode on them, with a suitable microcontroller you have a powerful system to know what is where! Much easier than RFID and much cheaper, also you can print labels as you want and they can be made to fit any size. Just for the record I have built such systems and currently working on a custom layout for a friend, I am not personally into the model railway world but I am a electronics engineer with 30+ years experiance