Railroad Preemption
Another type of preemption is railroad preemption. Traffic-signal-controlled intersections next to railroad crossings on one of the roads usually have this feature. Approaching trains activate a routine where, before the train signals and gates are activated, all traffic signal phases go to red, except for the signal immediately after the train crossing, which turns green (or flashing yellow) to allow traffic on the tracks to clear (in some cases, there are auxiliary traffic signals prior to the railroad crossing which will turn red, keeping new traffic from crossing the tracks. This is in addition to the flashing lights on the crossing gates themselves). After enough time to clear the crossing, the signal will turn. The crossing lights may begin flashing and the gates lower immediately, or this might be delayed until after the traffic light turns red.
The operation of a traffic signal while a train is present may differ from municipality to municipality. In some areas, all directions will flash red, turning the intersection into an all-way stop. In other areas, the traffic parallel to the railroad track will have a green light for the duration of the train while the other directions face a red light for the duration of the train.
Read more about this topic: Traffic Signal Preemption
Famous quotes containing the word railroad:
“People that make puns are like wanton boys that put coppers on the railroad tracks. They amuse themselves and other children but their little trick may upset a freight train of conversation for the sake of a battered witticism.”
—Oliver Wendell Holmes, Sr. (1809–1894)