Sometimes gates with predictor circuits will make the gates go up if a train slows of stops. If a train slows near a crossing sometimes the gates go up, then back down. The whole idea of the predictor is so the gates are down for just the required warning time. There are rules for predictor crossings about not speeding up more than 5mph within 3000' or so from the crossing. This is because if the train is going at 25 mph., the circuit will put down the gates about 20 seconds before the train hits the crossing. If it speeds up, then the gates may not be down long enough for the straggling motorists to clear.
The predictor technology was a great improvement. Before, a track circuit would have had to have been far enough out for the fastest train. Say on a hill, passenger trains may be able to make 60 mph. On that same hill, a freight may only be able to make 25 mph. Motorists would have to wait an extreme time period for the freight to hit the crossing, with the gates down for several minutes. This might bait the motorist. He might think that he shouldn't wait, just run the gate. It takes a long time for the train to reach the crossing, after the warning starts. Nest thing the passenger train comes along. The impatient driver decides to run it. With the fast passenger train, it is on him before he knows it................News reporters, police, ambulance, white sheets over people........
The predictor technology was a great improvement. Before, a track circuit would have had to have been far enough out for the fastest train. Say on a hill, passenger trains may be able to make 60 mph. On that same hill, a freight may only be able to make 25 mph. Motorists would have to wait an extreme time period for the freight to hit the crossing, with the gates down for several minutes. This might bait the motorist. He might think that he shouldn't wait, just run the gate. It takes a long time for the train to reach the crossing, after the warning starts. Nest thing the passenger train comes along. The impatient driver decides to run it. With the fast passenger train, it is on him before he knows it................News reporters, police, ambulance, white sheets over people........
