The gate down circuit ensures that the track clearance phase terminates when the gates

are horizontal

. The gate down circuit provides 2 separate benefits. First, it eliminates the preempt trap by ensuring track clearance green does not terminate prior to the gates descending. Otherwise, a red indication could occur at the traffic signal and another vehicle could queue back over the tracks. Second, it ensures that the track clearance green is not unnecessarily long when maximum right of way transfer time is needed.