Constant Warning Circuitry
Constant warning circuitry from the railroad company is recommended.
Constant warning circuitry along the rail can detect the speed of
an oncoming train and know when to preempt the traffic signal and
know when to drop a preempt call if a train stops on the approach.
Railroad circuitry is installed based on the fastest speed allowed
over the crossing, but not all trains will travel this speed over
the crossing.