Thats a good point hmmm. Try track prority marker and set them peridocly(SP) and pending how ambitious you are I would put them fairly close together. Along the track and the train should stay on it if you set the prority number to match the track meaning place a 1 track priority marker and set the consist to 1 as well and the train should follow the markers.
P.S. check out all the NJT threads floating around.