mdurdan wrote:the usual ditch lights here are constant on and flashing when horn sounds, that seems to be the norm.
You should take a look at Eyen's ditch lights or at G Trax ditch lights on the Amtrak unit, that aud to point you in the right direction

Well I'm stoked. Just did a search and found this
http://www.rail-videos.net/video/view.php?id=7883 which is bang in the middle of my route (the CCR starts to the right of that silo, Southern Loops are dead ahead and the other 15 odd miles of S-Line and marshalling yard in Conover behind the camera). So I've confirmed 3 things in the past 5 minutes... 1: The mainline on my route IS the S-Line (I was 99% certain but there was some debate) 2: The circus train runs through it (YAY!) and 3: There are trains running on it with flashing ditch lights.
So it's sufficed to say that I'll be pulling apart the P42 to figure it out like you suggest.