Grade crossing signals and gates are usually activated by senors or switches installed on the rails at a short distance from the crossing. The distance can be governed by several factors, including the track speed through that particular area. At a gated signal, for example, this allows the gates to fully drop before a train enters the crossing.
As a presenter for Operation Lifesaver, I am often called upon to address grade crossing mechanics in my discussions about crossing safety.
Here are some important things to keep in mind:
There are more than 260,000 grade crossings in the U.S.
About 40 percent of them have automated signals, that is, your combinations of bells, lights and gates or other barrier devices. these are known as actively-protected crossings, because there is an active device helping provide protection.
Actively-protected crossings mainly have flashing red lights. A very few older grade crossings, mostly in the West, have what are know as "wig-wag" signals, where the warning device, suspended on a vertical arm, swings back and forth like a pendulum.
The other 60 percent are known as passively-protected crossings. These usually have just the traditional crossbuck sign, the x-shaped sign the says "Railroad Crossing". At some locations, passively-protected crossings also have stop signs, just like at many road intersections. Incidentally, ALL public grade crossings have the crossbuck sign, whether they are active or passive.
There are also many "private" grade crossings where tracks cross driveways and other privately-owned roads. Crossbucks are not required at these crossings. Mostly, they have a small metal sign that identifies them as private crossings; some also have stop signs.
Train crews, by law, must whistle for EVERY crossing on their route, public and private, except where so-called "whistle bans" are in effect. The whistle (or air horn) signal that a train is approaching a crossing is:
Two long blasts, followed by a short blast, ending with a third long blast.
This is, in fact, a universal signal. I often tell people who attend my presentations that you can travel from Portland, Oregon (where I live) to Portland, Maine and everywhere in between, and hear the exact same whistle signal whenever a train nears a crossing.
Unfortunately, not everyone respects grade crossings. Every day there are at least 12 train-vehicle collisions somewhere in the U.S., about one every two hours. These collisions kill nearly 500 people a year and seriously injure several thousand more. That is why the Operation Lifesaver safety message is so important. Our organization operates in every state except Hawaii, so if you can contact your local OL representative, you can find out even more about it. A good place to start is at the OL national web site:
www.oli.org