Some locomotives have them coupled to the reverser so the correct end ditch lights come on when you head that direction. In some older locos, the ditch lights are manually shifted to different ends. The flashing is tied to the bell on some newer locos.
Per FRA Reg 49 CFR, sec 229,125: the ditch lights must be on if the engine is moving over a crossing at 20 mph or more. They can be on solid or flashing. Many railroads have them programmed to start flashing when the air horn or bell is sounded, and may keep flashing for about 30 seconds. This has been ammended several times since 1996.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
I have noticed in numerous videos of locomotives approaching that a lot of times the ditch lights are not on but come on as the locomotive approaches when blowing for a crossing and then they will be flashing alternatively. Other times they are both on steadily. Is there a standard or regulation as to when they are on or not or does it vary by railroad?
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