You know the signals along the line of the railroad—those gaunt, uncanny things that spell danger or safety to the men in the engine-cabs. A little while ago, we stood beside a man in the sun-filled tower of a great railroad terminal and watched him operate the most complicated switch and signal system in the land, watched him with the crooking of a finger upon the lever of an electric machine raise this blade, lower that, as he made new paths for the many trains, coming and going.
A plant of that sort is known as the interlocking. In its simplest form, it will guard a junction between two single tracks. The mast of the signal will rise, according to standard custom, at the right of the track in the direction of travel, and there will probably be two semaphore blades, the upper of which guards and signals the straight main-line or “superior” track, the lower, the diverging branch, known as the “inferior” track. The blade raised—automatically showing a red light—indicates that the main line is closed to the engineer. “Stop!” “Danger!” are the words it tells him. The blade lowered, a green light is automatically displayed, and the engineer knows that he can go ahead at full speed on the main line. The road is clear for him. The lower blade gives similar indications for the branch diverging line. Normally, both blades stand at “stop” and “danger,” and the one guarding the line for which the train is destined, is dropped only on the approach of the train, itself. In fact, to facilitate the movement of trains, these guarding signals—known to the signal experts as “home signals”—are generally interlocked with “distant signals” several hundred feet down the line, on which blades indicating the diverging tracks forecast the story that the “home signal” is to tell the engineer. The blade raised—by night displaying a white or safety signal—on the “distant signal” indicates that the line it guards is blocked at the “home signal,” and that the engineer must be prepared to bring his train to a full stop. Dropped—showing the green safety light—that particular line is open and ready, and the engineer can be prepared to pass the junction without a very great diminution of speed.
That is the fundamental rule of the signal. Some roads have experimented with other forms of indicators—disks of one sort or another, semaphore blades that turn upwards rather than drop. The devices are numerous, but the principle is the same. When the tracks begin to multiply, and the signals begin to multiply in even greater proportion, they are generally carried over the tracks on a light bridge construction—our English cousins call it a “gantry”—and a series of small semaphore masts built up from the bridge. One of these masts, or “dolls,” will be assigned to each track; and if there chances to be an unsignalled siding-track of little importance passing under the bridge, it will have its own “doll” rising from the bridge although quite devoid of semaphore blades. So it is all quite as clear as print to the engineer, even when forty or fifty lights blink at him from a single bridge. The signals tell their story to him quite as simply as to the man in the tower, who is setting their blades in accordance with his carefully arranged plans.
Where signals are not of this interlocking type, guarding some junction, railroad grade crossing, draw-bridge or other point of possible danger, they are likely to resolve themselves into the block system. This system, in a rather crude form, with the use of operators at each block-tower or way-station, has been in development for something less than thirty years upon the American railroad. In brief, it divides a line—usually double-tracked, but sometimes used by the so-called “staff” method upon a single-track road—into sections, or blocks, of from three to five miles each. On double-track under this system, no two trains, even though travelling in the same direction are permitted in the same block. At the entrance to each block stands a tall mast with two of the conventional signal blades. The upper of these raised denotes that a train is still in the block, and an engineer must stop his train and wait till it drops, before he can proceed. The lower blade, when raised, indicates that a train is in the second block ahead, and the engineer must proceed only with caution and expecting to find that block closed against him. It is all quite simple; and if the engineers followed the signals absolutely, there never could be any rear-end collisions on lines protected by block signals. As a matter of fact, there rarely ever are, although the engineers do take chances time and time again.
“Why should I stop for that thing,” said a veteran engineer on a fast express train as we went whirring by one of those upper blades raised and commanding us in a blood-red point of light to stop, “when I can look down this straight stretch and see they’re clear? Like as not something’s got into the mechanism of it and let her flop that way.”
Do not insult the intelligence of that engineer. A little while before, he had told us, with a deal of pride, that the rolling stock of “his road” placed end to end would reach from New York to Omaha, a distance of some 1300 miles. Keenest of the keen, he had a sort of contempt for a rule-book in such a case as that.
“Isn’t it sort of positive?” we began. “Good excuse anyway—”
“It is,” he shouted back, “but somehow it don’t go if you fall behind on your running time. We’re here to use ordinary good sense—and bring our trains in on time.”
And yet the railroad has a sharp way of insisting upon compliance with that book of rules by making, once in a great while, surprise tests. A signal is set at danger, without any more apparent reason than in the case just cited; a secret watch is kept, and judgment and discipline are visited upon the heads of the engineers who permit themselves to run past it.