Has anyone here ever heard of "island protection only" with regard to grade xings? As I kinda undertand it, this is a situation where the grade xing flashers are not activated until the train is literally at the road xing itself. Just the trackage in the road (the island) triggers the flashers. This would be useful on trackage that is like 5mph when a train stops before entering the roadway where the 20 second advance flasher warning isn't needed as on higher speed lines.
carajul wrote:Has anyone here ever heard of "island protection only" with regard to grade xings? As I kinda undertand it, this is a situation where the grade xing flashers are not activated until the train is literally at the road xing itself. Just the trackage in the road (the island) triggers the flashers. This would be useful on trackage that is like 5mph when a train stops before entering the roadway where the 20 second advance flasher warning isn't needed as on higher speed lines.I believe you are correct. Island circuits do this. Advance circuits activate the crossing in advance. The advanced circuitry is timed to the fastest a train can be moving on the tracks. The down side is if a train is heading at a slower speed, the crossing is activated regardless of the speed. Advanced circuits can be keyed up at certain crossings.
The best solution is the newer sensor crossings. No keying up required and they activate at a certain calculated time before the train reaches the crossing.