The operation of trains
We now turn to the last part of the story of railroads and their trains. We have learned something about the railroad track, the locomotives, and the cars, which run upon this track, and we have had a description of the most important features of railroad freight and passenger terminals. In other words, we have centered our attention upon the mechanism of the railroad, upon the physical equipment with which its work is done. So far we have said but little of how the railroad actually performs its work—the work of moving persons and things from place to place. It does this by means of moving trains. This chapter of our story is to tell something of how a railroad operates its trains.
Everybody knows that railroads have several different kinds of trains. They have passenger trains and freight trains, and some railroads have "mixed trains," which are trains made up of both freight cars and passenger cars. Many years ago nearly all railroads had mixed trains, but a mixed train is never seen now on an important railroad line. In out-of-the-way places, however, where there is not much trade or travel, the same trains often carry both passengers and freight. Then railroads have "work trains" which carry men and materials for railroad work. When new ballast is to be laid in a piece of track it is not unusual for a railroad to send out work trains, which carry the ballast and the men who unload it and put it where it is needed in the track.
It is no simple task to move trains over a railroad from terminal to terminal. Every train has a "crew" of course, which has direct charge of the train's movement. A train crew contains, first of all, an engineman and a fireman, who run the locomotive. Then there is a conductor, who is the "captain" of the train. On a passenger train the conductor collects fares and looks after the comfort of the passengers; on a freight train the conductor takes charge of the waybills,
directs the switching of cars and the loading and unloading of freight. Under the conductor, on both freight and passenger trains, are two or more "trainmen" or "brakemen." The passenger trainmen look after the heating and lighting of the cars, care for the signal lamps on the rear cars, call the stations before the train stops, and if the train is halted by an accident, they "protect" it both front and rear, by "flagging" other trains which may approach. The freight train brakemen help load and unload freight, couple and uncouple cars, help with the switching of cars, care for the train signals, and also protect
their trains, when necessary, by flagging. A passenger train which carries a baggage car also has a baggageman as a member of its crew. Pullman porters, dining car crews, barbers and messenger boys are often included in a train crew.
However competent and careful the crews of trains may be, it takes more than good train crews to get trains over a railroad. Do you remember what was said in the second chapter about the difference between a railroad and an ordinary highway? A railroad is sometimes called a non-steering highway, because trains are not steered, as automobiles and other highway vehicles are. Trains can not meet and pass at any place and at any time. The task of getting trains over a railroad requires the careful planning of train movements and constant direction from a central office. Each crew can not take its train along as it pleases, but must work under strict rules and under the orders of directing officials.
On a single-track railroad, with trains running in both directions, it is necessary for "opposing" trains to have definite meeting points. There must also be appointed places where fast trains may go ahead of slow ones. Where there are two or three or even four tracks, the problem of operating trains in two directions is somewhat less difficult than on single-track lines, but where more than one track is built, it means thai the railroad has heavy traffic and a large number of trains. So after all, the problem of moving trains from terminal to terminal may be just as difficult as on a one-track road where only a few trains are operated.
In order to simplify the problem of running trains, all railroads, except the very short ones, are divided into operating units, called "divisions." A division may be three of four hundred miles long or it may be only thirty or forty miles long. A division which has many trains and very extensive terminal facilities is likely to be much shorter than a division where the trains are few in number and the terminals small. Each division is operated as a unit, just as if it were a small railroad. Some trains run only between terminals on a single division. Some trains have their terminals on different divisions . A train with a long "run," such as the fast passenger trains between New York and Chicago, or between Chicago and Seattle, is operated over many divisions. It may change engines and crews several times in the course of its journey. But at any one time it is on only one division, and its movements are controlled by the officers having charge of that division.
A division is operated under the direction of a division superintendent, who is responsible for the movement of the trains. On most of our railroads the division superintendent also supervises the maintenance and repair of the track and the rolling stock of his division, but on some railroads his duty is only the supervision of train movements. The division superintendents are responsible to the "general manager," who is the chief operating officer of the entire railroad. On large railroad systems which have a great many divisions, there are several "general superintendents," each having under his control several division superintendents . On these systems the general superintendents are responsible to the general manager, while the division superintendents receive their orders from the general superintendents . The organization of a large railroad system is much like the organization of a large army. The colonels of the regiments are under the command of brigadier generals, who in turn are under the command of the major-general at the head of the army. If you live in a large city you may notice that the organization of your schools is something like the organization of a railroad. Each school building has a "principal." The principals of several schools are responsible to a "district superintendent," and the district superintendents are all responsible to the "superintendent of schools."
Each division superintendent of a railroad has several subordinate officers to aid him in his work. The two which help most in directing the movement of trains are the trainmaster and the chief dispatcher. The trainmaster has control of the train crews and sees that they observe the rules and obey the orders under which trains are moved. The chief dispatcher is the officer immediately responsible for the movement of all trains, and, aided by the train dispatchers, he issues the orders under which the train crews run their trains over the railroad. We shall talk about the train dispatcher after explaining other matters about train operation. If a division superintendent also has charge of maintenance and repair work on his division , he is assisted by a division engineer who supervises track repairs, and a master mechanic, who has general charge of the maintenance of cars and locomotives at the engine terminals and shops. The yardmasters and station agents on a division also are under the direction of the division superintendent. Another thing you must now learn, in order to understand how the movement of trains is directed, is that from an operating standpoint, a railroad has two distinct kinds of trains. They are "regular" trains and "extra" trains.
A regular train is a "scheduled" train, a train listed on the railroad time-table. A railroad has certain trains which are operated each day. They have definite times of leaving their terminals, definite times to make stops at stations, and definite limes for arrival at the terminals where they complete their runs. These are the regular trains. They are all numbered. The list of times at which a regular train is due to arrive at and leave stations is called the train's "schedule." The printed schedules of the regular trains operating on a railroad division form the "time-table" of that division. You have probably all seen passenger train time-tables, such as one may obtain at a passenger station. These are not like the official railroad time-tables, which show the schedules of all regular trains, both freight and passenger.
If you have a friend who works on a railroad you should get him to show you an official railroad time-table. You will find many things of interest in the ordinary passenger train time-table. One thing you may have noticed already is that all trains in one direction have even numbers, while the trains in the opposite direction all have odd numbers. All regular trains on a railroad are divided into "classes." There may be two or three, or even four classes of trains. When only two classes, the first-class trains are the passenger
trains, and the second-class trains are the freight trains. On some railroads there are two classes of passenger trains, the first-class trains being the fast expresses, which have long runs and make few stops, while the second-class trains are the local or "accommodation" trains, which stop at all stations. In the same way there may be different classes of freight trains, the fast trains carrying livestock or perishable fruit and vegetables being of a higher class than the local freight trains, which stop at small stations to load and unload less-than-carload freight and pick up and deliver single cars.
"Extra" trains are trains which are not scheduled in the railroad time-tables. Extra freight and passenger trains are both quite common on our large railroads. Work trains and wreck trains are always run as extra trains.
The extra passenger trains with which we are most familiar are the Sunday and holiday excursion trains. Many of the trains which carry crowds to conventions, fairs and football games are extra trains. We usually speak of extra passenger trains as "special" trains. When a large number of persons want to make a railway trip together they hire a special train. Sometimes you will read that some wealthy person has hired a special train so as to make a speedy journey. When the President makes an extended tour about the country he usually travels in a special train.
Most of our railroads have more extra freight trains than extra passenger trains. Every railroad has its regular freight trains, which are scheduled in its time-tables, but on the larger railroads it is customary to move ordinary freight, such as coal, ore, lumber, and other cheap bulky articles, as it accumulates at terminals and stations. The number of freight trains varies with the amount of freight to be moved. When traffic is heavy the number of extra freight trains is large, and when traffic is light fewer trains are needed. One of the duties of the chief dispatcher is to know about traffic conditions on his division and order extra trains as they are needed.
Now the operation of a railroad division is planned first of all to take care of the regular trains. The schedules of all these trains are carefully worked out, so that, if the trains move "on time," opposing trains meet where there are tracks for passing, and fast trains overtake and pass slow trains with no delay to either. Trains of a higher "class" are "superior" to trains of lower classes, and at passing points on single track lines the trains of the lower class take the siding to make way for the "superior trains." Most railroads have a rule providing for "superiority by direction." All trains moving in one direction are superior to trains of the same class moving in the opposite direction. Where there are two classes of trains one consisting of passenger and one of freight trains, the freight trains must always take the siding and make way for passenger trains, but where two passenger trains, or two freight trains meet—two trains of the same class—that one keeps the main track which is given superiority by direction. The rules establishing superiority of trains by class and by direction do away with all confusion as to how the crews should handle their trains at designated passing points.
Now, if a railroad had only regular trains—no extras— and if these regular trains were always on time, the operation of the trains over a railroad division would be a fairly simple task. All the operating officials would have to do would be to plan the schedules properly, draw up the rules for the train crews, and there would be little difficulty connected with train movement.
But there are two big "ifs" in the way. Unfortunately, the regular trains are not always on time, and, as you were told before, it is customary for all railroads to have extra trains. The big problem of operating the trains on a division comes when the regular trains are delayed and when a number of extra trains are running. How are the movements of trains guided and controlled when the regular trains do not keep their schedules, and when provision must be made for trains that have no schedules at all?
It is here we come to the work of the train dispatcher. It is a dispatcher's duty to guide the movement of trains over a division. On some railroads large divisions are broken up into "districts" or "subdivisions" and the work of directing train movements over the division is done by several train dispatchers , each watching over a single subdivision. The train dispatcher controls train movements by giving "train orders" to the engineers and conductors of the trains. He sends these orders by telegraph or by telephone to operators at stations along the division, and the operators deliver the orders to the enginemen and conductors.
In the early days of the railroad there was no telegraph or telephone. The railroads did not have extra trains. All trains were regular. When a train on a single-track railroad reached a point where it was scheduled to meet another train, it had to wait until the other train came. Sometimes an accident would halt the other train, and there would be many hours of delay for the train waiting at the meeting point. Some roads had rules permitting a train to move ahead after waiting a half-hour at a meeting point, but whenever a train proceeded under such a rule, it had to be preceded by a flagman walking far enough ahead to give ample protection against collision with the opposing train. If trains met between sidings, the train nearest a siding had to back up and let the other pass. You can imagine how slow travel became when a train broke down on a single-track railroad.
The invention of the electric telegraph made it possible to do away with the long delays caused by the failure of a train to reach a meeting point at the scheduled time. The first use of the telegraph in directing the movement of trains came about in an interesting manner.
In 1851 Charles Minot, the general superintendent of the New York and Erie Railroad Company, was making a trip on a westbound train to Port Jervis, New York. His train reached Turner's, now Harriman, where it was scheduled to meet an eastbound train. The eastbound train was not there. There was a telegraph office near the siding, and Minot sent a message to Goshen asking the agent if the eastbound train had reached that town. The agent replied at once that it had not.
Thereupon Minot telegraphed that when the train arrived there it should be held until he sent further orders for its movement. He then told the engineer of his own train to go
ahead. The engineer feared an accident and refused to do so. Minot then took the engineer's place and ran the train himself . At each station he came to he made further telegraphic inquiries about the delayed eastbound train. He finally made arrangements for passing it at a siding a few miles east of Port Jervis, and brought his own train into Port Jervis on time, instead of many hours late, as it would have been had it waited at the scheduled meeting point.
The use of the telegraph showed the way to a greatly improved method of running trains, and marked the beginning of the modern system of train dispatching. The telegraph became one of the most important aids to railroad operation. Every railroad put up telegraph lines and placed telegraph instruments in all railroad stations. You have all seen the telegraph poles and wires along the right of way of a railroad, and many of you have watched station operators receive and send messages by means of clicking telegraph instruments. Today many railroads use the telephone instead of the telegraph for train dispatching. And in many offices, while the electric telegraph is still used, it is a printing telegraph. The "brass-pounder" has made way for the machine.
On every railroad division there is always a train dispatcher at work. From every station he receives reports of passing trains. He knows at all times the location of every train on his division. When a train gets "late," or when an extra train is started, it is his business to give the orders which will permit the trains to pass over the division with as little delay as possible . He gives orders for changes of schedules, orders appointing new meeting places for opposing trains, orders for shifting trains from track to track on lines where more than one track is available. He directs the movement of trains just as a general directs the movements of the troops of an army, keeping trains on the move as much of the time as possible, and keeping them out of one another's way. His orders for the movement of trains are supreme. Any "right" which he gives by train order takes rank over "superiority" by class or by direction .
Nobody on a railroad has a position of greater responsibility than a train dispatcher. His work requires quick thinking, quick acting, and above all absolute accuracy. The slightest mistake on the part of the dispatcher may cause a terrible
accident. If he permits a train to leave a station on a singletrack line, forgetting that he has permitted an opposing train to use the track from the next station ahead, there is almost sure to be a collision and a wreck, unless the engineers see the danger in time to stop.
A train dispatcher is permitted to work only eight hours a day. His hours of duty are short because a tired person may make mistakes. Each dispatcher makes a complete record of the movement of trains on his division and keeps a copy of all the train orders which he sends, for the guidance of the dispatcher who relieves him.
While it is vitally necessary that the dispatcher make no mistakes in giving train orders, it is equally necessary that the enginemen and conductors who receive the orders understand them and obey them. To safeguard the movement of trains by train orders the railroads have very strict rules for sending and receiving orders. The operators who receive orders for delivery to trains must write them down and then repeat them to the dispatcher. If a train order is of a kind that misunderstanding it or disobeying it would cause a collision , the conductor to whom it is sent must read it aloud to the operator and then sign it, and the operaior must telegraph the signature to the dispatcher. The conductor then delivers a copy to the engineman, and the engineman reads it aloud to the conductor before he starts his train. The engineman must show train orders to his fireman and a conductor must, if possible, show orders to the trainmen. Everything possible is done to let the train dispatcher be sure that the operator has received a train order correctly, that it has been delivered to the persons to whom it is addressed, and that these men understand the exact meaning of the order. Once in a while an accident occurs because an engineman misunderstands an order or forgets to obey it. But mistakes, either on the part of train dispatchers or on the part of train crews, do not happen frequently.
The system of controlling train movements entirely by time-tables and train orders is called the "time interval system ," because its chief purpose is to keep trains apart, when running, by a certain amount of time. Under this system all trains are expected to reach meeting points or passing points in ample time for the inferior train to get out of the way of the superior train.
The time interval system has certain faults. Between telegraph stations the crew of one train has no sure way of knowing the location of a train ahead, which is running in the same direction. Train rules provide that trains running in the same direction must keep at least five minutes apart, and that a train following a passenger train must keep at least ten minutes behind it. If trains keep to their schedules and run "on time" it is not very difficult for two trains to stay the proper distance apart under the time interval system. But if a train in front
should break down and stop, or if it should begin to lose speed and run "late," there is danger of a collision if the train in the rear is not stopped or its speed checked. The rules of operation are very strict with regard to a situation of this kind. Whenever the train in front makes an unexpected stop, a trainman is required to hasten back along the track to "protect" his train. In the daytime the llagman carries a red flag, several torpedoes and some fusees; at night a red and a white lantern and torpedoes and fusees. The torpedo is a small disk-shaped metal box containing an
explosive. The box has a short metal clip on each side. The torpedo is placed on top of the rail, and is held in place by the two clips which fold under the head of the rail. A locomotive passing over a torpedo causes it to explode, and the report warns the engineman to stop his train. A fusee looks something like a Roman candle. It does not shoot balls of fire, however, but burns for several minutes with a brilliant red or yellow light. In all kinds of weather, day or night, the flagman of a train that has made an unexpected stop is able by one method or another, or by several methods, to give a signal to an approaching train. If the train in front merely loses speed, and there is danger of its being overtaken by a following train, the flagman drops lighted fusees along the track from the rear of the train, and these fusees warn the following train to proced with caution.
In spite of the strict rules about protecting trains by flagging, there have been a great many rear-end collisions between trains operated under the time interval system. Sometimes the accidents have been due to the failure of flagmen to go back far enough, or to go back at all; or they have been due to the failure of enginemen to see or hear the signals of flagmen, or to their failure to heed the signals. Under the time interval system of train operation there have also been many head-on collisions between opposing trains, due to the mistakes of train dispatchers in giving train orders, the mistakes of operators in receiving or delivering orders, and to mistakes of train crews in reading their orders and in reading their time-tables.
For many years the time interval system was the only method of controlling train movement. But as traffic became heavier and more trains were run on our railroads it was seen that something should be done to make train operation safer. About seventy-five years ago a great improvement was introduced in the methods of directing train movements. A new system was devised, known as the "space interval" or "block" system. Under this system a railroad is divided into a number of short sections or "blocks." A fixed signal is placed at the beginning of each block to tell the engineman of an approaching train if the block is occupied by another train. With this system trains can be "spaced" with certainty. They can be kept a definite distance apart, if signals are carefully observed and obeyed. They can not be spaced with certainty under the time interval system. Our railroads still use time-tables and train orders to guide the movement of trains, but in addition our larger and more important railway lines have "block signals."
The block signal serves two very useful purposes. First of all, it is a fine safety device, which has done much to decrease the danger of train collisions. In the second place, it permits a railroad to operate a greater number of trains, because with block signals, trains can be run closer together. It would be impossible for many of our railroads to transport their numerous trainloads of passengers and freight if they did not have block signals.
There are several kinds of block signals. The most common type is the "semaphore," which gives signal indications by day by means of a movable arm and by night by means of colored lights. The semaphore arm is mounted on a tall post beside the railroad track, or on a short post, supported above the track by a "signal bridge." The arm consists of a metal or wooden blade about four feet long, fastened to a metal casting, which turns on a pivot. This metal casting contains a "spectacle," which holds circular pieces of colored glass called "roundels." A lamp on the signal post shines through the roundels and gives the colored light signals at night.
In another type of block signal colored lights give the signal indication both day and night. Each light of the signal has a heavy shade above it, and the light can be seen quite clearly by day. You have probably all seen colored light signals of much the same kind at highway crossings, where they are used to direct automobile traffic. Another type of block signal is known as the "position light" signal. The indication is given just as by a semaphore, short rows of white lights taking the place of a semaphore blade.
The first block signals were operated entirely by hand, and on some of our railroads they are still operated in this manner.
A signal tower stands beside the track at the beginning of each block, with a man in charge of the signal. All the towers are connected by telegraph or telephone. Signals are kept normally in a stop position. When a train approaches the tower the signalman notifies the man at the next tower, who, if the block is clear of trains, reports so at once. The signal is then set to admit the train to the block, and is set at stop again as soon as the train has passed. This system of block signalling is called the "manual system."
Block signal operators are sometimes careless, and admit trains to blocks occupied by opposing trains. To guard against the carelessness of operators the "controlled manual" system of block signalling was introduced a good many years ago. Under this system the signals of the towers are "locked" together electrically, and the operator at one tower can not change the position of his signal without the help of the signalman in the next tower. The controlled manual signal is just like a door with two locks, the keys of which are carried by two different persons. The door can not be unlocked and opened unless both persons use their keys.
The radio telephone will be helpful in speeding trains over tracks controlled by manual block signal systems. A train may be permitted to enter a block already occupied, and proceed under full control. When notified by the operator at the next tower that the train ahead has left the block, the engineer can resume speed. Less time will be lost in waiting for a block to be cleared.
While the manual and the controlled manual systems of block signalling are still quite widely used, the most important type of block signal, and the type which is found on the main lines of all our great railroads, is the automatic electric block signal. Automatic electric signals are operated by the trains themselves, and they need no signalmen in constant attendance . In each block an electric current passes through the the rails—through a "track circuit." If you were ever on a railroad having automatic electric signals, you may have noticed that the rail joints are all "bonded," that is, there are copper wires or bonds extending between the webs of the rails at each joint. These bonds carry the track current from rail to rail. At one end of the block the rails are connected with the signal mechanism by underground wires, while at the other end they are connected with the battery which supplies the current for the track circuit. Each block is insulated from
the blocks next to it. If you should ever stand near an automatic electric block signal, be sure to notice the insulating material between the ends of the rails near the signal. While the electric current flows through the track circuit the signal
remains in a "block clear" position. When a train enters the block it "short-circuits" the current flowing through the rails. This sets in operation another electric current in the signal mechanism, which sets the signal at the stop position. An interesting feature of the automatic electric signal system is that the breaking of a rail in the track interrupts the current of
the track circuit and sets the signal at the entrance of the block just as a train in the block would set it. Now, the important thing about a signal is what it means to the engineman on the train. What messages do block signals
give? Different railroads have different systems of signalling. By the use of two or three semaphores on a single signal post, it is possible for a block signal to give a number of messages. Some signalling systems are somewhat complicated. We shall
not try to understand them all. We shall talk only about the messages given by the "three position" semaphore signal. This signal is perhaps the most common and the best known of block signals.
The semaphore blade of this signal has three different indications ; it can give three different messages. In a horizontal position it means, "stop, there is a train in the block ahead"; in a diagonal position it says, "caution, there is no train in the block ahead, but there is a train in the second block. Be prepared to stop at the next signal"; in a vertical position it says, "proceed, the next two blocks are clear."
On some railroads the semaphores are constructed so that the blades move in the "lower quadrant," that is, they move downward in passing from the horizontal to a diagonal or vertical position. The "upper quadrant" signal is more common , however, the signal blade moving upward from the horizontal to the diagonal and vertical positions. When the semaphore blade moves to a horizontal position it brings a red roundel in front of the signal lamp; a diagonal position places a yellow roundel before the lamp; while the vertical position brings a green glass. At night, therefore, a red light means stop, a yellow light caution, and a green light proceed.
Where manual and controlled manual signals are in use a train may not pass a block signal, which is in the stop position, without the consent of the signal man in the tower. On a double track railroad having automatic signals, a train must stop on approaching a stop signal, but the engineer can at once take his train forward, moving very slowly and expecting to be compelled to stop at any moment by a train ahead. The engineer is permitted to advance beyond an automatic stop signal in this manner, because the signal may be in the stop position because of a broken rail or because the signal mechanism is out of order. If the signal is at stop for either of these reasons, a member of the train crew reports to the dispatcher as soon as possible, and orders are given to have the track or the signal repaired.
Have you ever watched an automatic block signal work? If you haven't, you must be sure to do so. Stand near the signal post while the track is clear and the signal blade in a vertical position. Along comes a train. As soon as the engine enters the block, the semaphore blade moves until it becomes horizontal. On goes the train. In a few moments, after the train has passed entirely out of sight, the signal suddenly begins to move, and slowly goes to the diagonal position. The train has entered the next block ahead. A few more moments and again the signal moves, going back to the vertical position once more. The track is clear now for two blocks ahead. Day and night, as trains pass by, the signal arm moves up and down, always giving its messages to the enginemen, so that they may space their trains and avoid all danger of accidental collision.
Block signals have done much to increase the safety of train operation. But it must nevertheless be said that collisions still occur now and then on roads which have block signals, and occur when the signals are in perfect order and are properly operated. These accidents happen because enginemen are not always careful. The railroads have strict rules about the observance of block signals, just as they have strict rules about all other matters of train operation, but the rules are not always obeyed.
Sometimes bad weather causes trouble. On dark, foggy nights signal lights are hard to see. When the signals can not be seen an engineman is required by rule to move his train slowly and carefully. He does not always do this. Not wanting to bring his train in late, he hurries along, goes past a stop signal without seeing it, and crashes into another train. Sometimes an engineman goes to sleep, and an accident occurs before the fireman, busy with other duties, is aware of the danger.
When an engineman sees a signal in the caution position, he knows that the second block ahead is occupied. The rules of the railroad require him to reduce speed and be prepared to stop at the next signal. Pretty soon he sees the next signal, and it is also in the caution position. On he goes, passing one signal after another, all of them at caution. The train in advance is keeping something more than a block ahead, and the engineer of the following train expects that it will continue to do so. Instead of approaching the "next signal" prepared to stop, he drives on at full speed. Then something happens.
The train ahead is compelled to stop by a broken air hose or some other trifling accident. It stops with its rear car just beyond a block signal. If the engineman of the following train were obeying rules, approaching the "next signal" prepared to stop, there would be no accident. But he is disregarding the rules. He brings his train thundering along. Too late he sees the signal at stop, instead of at caution, as he had expected. The flagman of the train ahead has not had time 10 get back, or if he has had time, perhaps he has neglected to go back far enough. He may ask himself what block signals are for if they are not to save the flagman's legs. The following train drives onward. There is a grinding of brakes, but the speed is too great. The train can not stop, and on it goes, crashing into the rear of the stopped train. The signals have worked perfectly, but nevertheless there has been a wreck.
What can be done to prevent accidents when block signal indications are neglected by train crews? Our railroads are trying to solve this problem by the use of automatic train stops and speed control devices. Ingenious electrical contrivances have been invented to bring a train
to a stop without the action of the engineman, when he runs past a warning signal. While these inventions have not been developed to such an extent that they are perfectly satisfactory, they are sufficiently reliable that our government has required the railroads to begin to use them. On a railroad equipped with automatic stops, should an engineman run his train by a danger signal, the stop device causes the air brakes to be applied. It is only a question of time until all our great main lines of railroad will be equipped with a device which will make train collisions virtually impossible.
In developing automatic train control mechanisms signal engineers have in recent years perfected an entirely new safety device of the greatest value. This is the locomotive cab signal. It is a small colored light signal, placed directly in front of the engineer's seat, and it gives the same signal indications that are given by the block signals along the track. The cab signal can not be obscured by snow or rain or fog, and it tells the engineer at all times whether or not there is another train close ahead. The use of high speed trains during the past few years has made it necessary for several railroads to change their whole
signal installations. A fairly heavy train running at the rate of eighty or ninety miles an hour can not be stopped, even with the best of brakes, as quickly as a train that is running at half that speed. Some blocks were found to be so short that before one of the new fliers could be made to respond to the indication of the signal it would be running through the next signal. This meant either that blocks had to be made longer or that signals had to be installed which would give information concerning trains ahead for three or four blocks instead of two. On some railroads the block signal posts may carry two or three semaphores instead of one. Combinations of semaphore positions, by day, and of red, green and yellow lights
by night, can convey a greater variety of messages to the engineer of an approaching train than can be conveyed by a single-arm signal. If signals are obeyed, the fastest trains are operated with safety. The use of improved signals is more advantageous than the lengthening of blocks on roads where traffic is dense, because it permits the operation of a larger number of trains.
The radio telephone and other means of wireless communication are today being used to promote greater safety in train operation. It has already been told how helpful wireless communication has become in railroad yards, where much time can be saved when yardmasters and hump conductors can maintain constant connection with the enginemen and other crew members of switching locomotives. All the best passenger
trains and many freight trains have radio telephones for intratrain communication, and many freight trains now have a "carryphone" or "walkie-talkie," which enables a flagman or brakeman to get off the train and still have speaking connection with the members of the crew remaining aboard the train, with the crews of nearby trains, or with wayside stations withing a distance of fifteen miles. With the radio telephone a train dispatcher can communicate at any time with the trains moving on his division, and the crew of one train can be kept informed of the movement and position of other trains. If a train has to stop suddenly or reduce speed because of some mishap, the crew of a following train can be notified promptly and the danger of a rear-end collision avoided. Electronic devices have been developed that automatically give signals in the dispatcher's office to indicate the position of trains. Under the system long in use the dispatcher's knowledge of train movements came entirely from the OS (out of station) reports of operators at those offices where a telephone or telegraph instruments were maintained. Now he can receive indications of passing trains by automatic contrivances located at any number of points between telegraph offices. The dispatcher has much more knowledge of the location of all the trains under his jurisdiction, and can more readily plan for their future movements, if necessary to send out train orders. It may be that at some time in the future train dispatchers will send their orders and other messages directly to train crews on moving trains, instead of transmitting them through operators along the railroad line. There is no reason why the movements of trains should not be controlled directly from the dispatcher's office just as the flight of airplanes is direc ted from the control room of an airport. Some people profess to believe that we shall some day have trains without enginemen just as we have pilotless airplanes. Trains will all be subjected to "remote control."
There is another important safety device which you must hear about. Our railroads use it at points where several tracks come together or where tracks cross one another, and at other places where special care must be taken to prevent accidents to moving trains. This device is the "interlocking machine." Switches and signals or signals and train derailing devices are
so interlocked with one another that when any one route is opened for the movement of trains, it is physically impossible to set signals and switches for a train on a conflicting route. A simple example of interlocking is that usually found at the approach to a railroad drawbridge—a bridge which can be opened to let boats pass. Near the entrance to the bridge is a "home" signal. Several hundred yards back from the home signal is a "distant" signal. You can usually recognize the semaphore of a distant signal by the fact that the end of the blade is V-shaped, like a fish tail. The engineman on a train sees the distant signal first as he nears the bridge. If it is in Lhe stop position, he knows that the home signal also is in the stop position, and he must halt his train before reaching it. If the distant signal is "clear" the home signal too is in the proceed position. The bridge and the signals are interlocked in the following manner. The bridge can not be opened until after the home signal is set at stop, and the home signal can be set at stop only after the distant signal has been placed in the stop position. Once the bridge is opened, both signals are locked in the stop position until the bridge is closed. After it is closed the distant signal can not be moved to the proceed position until the home signal is "cleared."
Interlocking plants are always found at the entrance to large passenger stations where many trains arrive and depart each day. The switches and signals are all operated from an "interlocking tower." In small plants they are moved by human effort, being connected by long pipes or wires with the levers in the tower. In large plants they are moved by electricity or by compressed air, and the tower levers consist of a large number of electric switches. Some interlocking plants are automatic in their operation, that is, the switches and signals are actuated in their movements by the trains themselves, much in the same way that automatic block signals are operated.
Though extremely intricate and complicated, an interlocking machine is one of the most accurate and reliable machines in use. It does not permit mistakes to be made. It is impossible for an operator to set switches and signals in such a manner that trains will collide, provided the signal indications are observed and obeyed. In some interlocking plants, if an engineman disregards the signals and moves his train forward over a closed route his train is derailed, but derailing devices are now seldom used. Engineers know when they are approaching an interlocking plant, and they are supposed to be extremely careful. If there is an interlocking tower near where you live, try to get permission to visit it, and have the operator tell you about the principles of interlocking and show you how the interlocking machine works.
The most recent, and in some respects the most interesting, device for controlling the movements of trains is known as "centralized traffic control." On many railroads there are sections where the traffic is quite dense. There may be one or more diverging branch
lines having several daily trains to and from the main track; there may be one or more crossings with other railroads; and there may be several turnouts, where main line trains pass one another.
Where the trains in such a section are operated only by schedule and by train order, their movements are somewhat delayed. Trains must stop while switches are thrown by hand, then start up and stop again while switches are closed and the brakemen run to overtake their trains. And much time may be lost while trains wait for the appearance of opposing trains at passing sidings.
With centralized traffic control all train movements in the section under such control are governed by signal indications only. The signals and switches are all operated electrically from a single tower. In this tower there is a large panel upon which is shown the layout of all tracks in the controlled section. There is a separate lever for each switch and signal. When a train enters the controlled section a small light flashes on the panel, and as it moves along other lights flash to show its location. It is the business of the operator of the traffic control machine to keep the trains moving with as little delay as possible. He does this by shifting trains from track to track, making the necessary signal and switch movements. Centralized traffic control saves a great deal of time. The sections of track under the control of a single operator may be many miles in length. The switches and signals are all interlocked so that it is impossible for an operator to show signals admitting two trains to the same track. If you ever have an opportunity to visit a tower having centralized traffic control equipment, you must be sure to do so.
The movement of trains on a railroad is a wonderful example of how order and system help in the performance of difficult tasks. The transportation of the passengers and freight of this country requires a large number of trains every day. Many of these trains must move very rapidly, and all possible care must be taken to see that every train is operated safely. It is only because the work is well organized and well directed that our fast and our local freight trains, our local and our express passenger trains can come and go day after day throughout the year.
The organization of train movements has come about by a process of growth and development. Since the first railroad was built there has been as much change in the system of directing trains as there has been in the railroad track and in the locomotives, cars and terminal facilities. If the builder of the "Rocket" were still living, he would probably be no more interested in one of our huge locomotives than in the system of railroad operation, under which our fine passenger trains, such as the Twentieth Century, the Broadway Limited, the Overland, the Dixie Flagler, and the Sunshine Special fly along the rails without interference from the dozens of slower pas senger and freight trains which use the same tracks.