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RAILROAD ACCIDENTS.

182

CHAPTER XVIII.

INTERLOCKING.

IN their management of switches, especially at points of railroad convergence where a heavy traffic is concentrated and the passage of trains or movement of cars and locomotives is unceasing, the English are immeasurably in advance of the Americans; and, indeed, of all other people. In fact, in this respect the American managers have shown themselves slow to learn, and have evinced an indisposition to adopt labor-saving appliances which, considering their usual quickness of discernment in that regard, is at first sight inexplicable. Having always been accustomed to the old and simple methods, just so long as they can through those methods handle their traffic with a bearable degree of inconvenience and expense, they will continue to do so. That their present method is most extravagant, just as extravagant as it would be to rent two houses or to run two steam engines where one, if properly

THE CANNON STREET STATION. 183

used, could be made to suffice, admits of demonstration;—but the waste is not on the surface, and the necessity for economy is not imperative. The difference of conditions and the difference in results may be made very obvious by a comparison. Take, for instance, London and Boston—the Cannon street station in the one and the Beach street station in the other. The concentration of traffic at London is so great that it becomes necessary to utilize every foot of ground devoted to railroad purposes to the utmost possible extent. Not only must it be packed with tracks, but those tracks must never be idle. The incessant train movement at Cannon street has already been referred to as probably the most extraordinary and confusing spectacle in the whole wide circle of railroad wonders. The result is that in some way, at this one station and under this single roof, more trains must daily be made to enter and leave than enter and leave, not only the Beach street station, but all the eight railroad stations in Boston combined.*

* "It has been estimated that an average of 50,000 persons were, in 1869, daily brought into Boston and carried from it, on three hundred and eighty-five trains, while the South Eastern railway of London received and despatched in 1870, on an average, six hundred and fifty trains a day, between 6 A.m. and 12 P.M. carrying from 35,000 to 40,000 persons, and this too without the occurrence of a single train accident during the year. On one single exceptional day eleven hundred and eleven trains, carrying 145,000 persons, are said to have entered and left this station in the space of eighteen hours."—Third Annual Report, [18721 of Massachusetts Railroad Commissioners, P.141.

The passenger movement over the roads terminating in Boston was probably as heavy on June 17, 1875, as during any twenty-four hours in their history. It was returned at 280,000 persons carried in 641 trains. About twice the passenger movement of the "exceptional day" referred to, carried in something more than half the number of trains, entering and leaving eight stations instead of one.

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During eighteen successive hours trains have been made to enter and leave this station at the rate of more than one in each minute. It contains four platforms and seven tracks, the longest of which is 720 feet. As compared with the largest station in Boston (the Boston & Providence), it has the same number of platforms and an aggregate of 1,500 (three-fifths) more feet of track under cover; it daily accommodates about nine times as many trains and four times as many passengers. Of it Barry, in his treatise on Railway Appliances (P. 197), says: "The platform area at this station is probably minimised but, the station accommodates efficiently a very large mixed traffic of long and short journey trains, amounting at times to as many as 400 trains in and 400 trains out in a working day.*"

The American system is, therefore, one of great waste; for, being conducted in the way it is-that is with stations and tracks utilized to but a fractional part of their utmost capacity it requires a large number of stations and tracks and the services of many employees. Indeed it is safe to say that,

* The Grand Central Depot on 42d Street in New York City, has nearly twice the amount of track room under cover of the Cannon street station. The daily train movement of the latter would be precisely paralleled in New York, though not equalled in amount, if the 42d street station were at Trinity church, and, in addition to the trains which now enter and leave it, all the city trains of the Elevated road were also provided for there.

PRIMITIVE WAYS 185

judged by the London standard, not more than two of the eight-stations in Boston are at this time utilized to above a quarter part of their full working capacity; and the same is probably true of all other American cities. Both employees and the travelling public are accustomed to a slow movement and abundance of room; land is comparatively cheap, and the pressure of concentration has only just begun to make itself felt. Accordingly any person, who cares to pass an hour during the busy time of day in front of an American city station, cannot but be struck, while watching the constant movement, with the primitive way in which it is conducted. Here are a multiplicity of tracks all connected with each other, and cars and locomotives are being passed from one to another from morning to night. A constant shifting of switches is going on, and the little shunting engines never stand still. The switches, however, as a rule, are unprovided with signals, except of the crudest description; they have no connection with each other, and during thirty years no change has been made in the method in which they are worked. When one of them has to be shifted, a man goes to it and shifts it. To facilitate the process, the monitor shunting engines are provided with a foot-board in front and behind, just above the track, upon which the yard hands jump, and are carried about from switch to switch, thus saving the time they would occupy if they had to walk. A simpler arrangement could

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not be imagined; anyone could devise it. The only wonder is that even a considerable traffic can be conducted safely in reliance upon it.

Turning from Beach to Cannon street, it is apparent that the train movement which has there to be accommodated would fall into inextricable confusion if it was attempted to manage it in the way which has been described. The number of trains is so great and the movement so rapid and intricate, that not even a regiment of employees stationed here and there at the signals and switches could keep things in motion. From time to time they would block, and then the whole vast machine would be brought to a standstill until order could be reestablished. The difficulty is overcome in a very simple way, by means of an equally simple apparatus. The control over the numerous switches and corresponding signals, instead of being divided up among many men stationed at many points, is concentrated in the hands of two men occupying a single gallery, which is elevated across the tracks in front of the station and commanding the approaches to it, much as the pilot-house of an American steamer commands a view of the course before it. From this gallery, by means of what is known as the interlocking system, every switch and signal in the yard below is moved; and to such a point of perfection has the apparatus been carried, that any disaster from the misplacement of a switch or the display of a wrong signal is rendered impossible. Of this Cannon

THE ORIGIN OF INTERLOCKING. 187

street apparatus Barry says, "there are here nearly seventy point and signal levers concentrated in one signal house; the number of combinations which would be possible if all the signal and point levers were not interlocked can be expressed only by millions. Of these only 808 combinations are safe, and by the interlocking apparatus these 808 combinations are rendered possible, and all the others impossible."*

It is not proposed to enter at any length into the mechanical details of this appliance, which, however, must be considered as one of the three or four great inventions which have marked epochs in the history of railroad traffic.+ As, however, it is but little known in America, and will inevitably within the next few years find here the widest field for its increased use, a slight sketch of its gradual development and of its leading mechanical features may not be out of place. Prior to the year 1846 the switches and signals on the English roads were worked in the same way that they are now commonly worked in this country. As a train drew near to a junction, for instance, the switchman stationed there made the proper track connection and then displayed the signal which indicated what tracks were opened and what closed, and which line had the right of way;

* Railway Appliances, p. I 13.

+ A sufficiently popular description of this apparatus also, illustrated by cuts, will be found in Barry's excellent little treatise on Railway Appliances, already referred to, published by Longmans & Co. as one of their series of text-books of science. 

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and the engine-drivers acted accordingly. As the number of trains increased and the movement at the junctions became more complicated, the danger of the wrong switches being thrown or the wrong signals displayed, increased also. Mistakes from time to time would happen, even when only the most careful and experienced men were employed; and mistakes in these matters led to serious consequences. It, therefore, became the practice, instead of having the switch or signal lever at the point where the switch or signal itself was, as is still almost universally the case in this country, to connect them by rods or wires with their levers, which were concentrated at some convenient point for working, and placed under the control of one man instead of several. So far as it went this change was an improvement, but no provision yet existed against the danger of mistake in throwing switches and displaying signals. The blunder of first making one combination of tracks and then showing the signal for another was less liable to happen after the concentration of the levers under one hand than before, but it still might happen at any time, and certainly would happen at some time. If all danger of accident from human fallibility was ever to be eliminated a far more complicated mechanical apparatus must be devised. In response to this need the system of interlocking was gradually developed, though not until about the year 1856 was it brought to any considerable degree of perfection. The whole

THE ELIMINATATION OF BLUNDERS. 189

object of this system is to render it impossible for a switchman, whether because he is weary or agitated or actually malicious or only inexperienced, to give contrary signals, or to break his line in one way and to give the signal for its being broken in another way. To bring this about the levers are concentrated in a cabin or gallery, and placed side by side in a frame, their lower ends connecting with the switch-points and signals by means of rods and wires. Beneath this frame are one or more long bars, extending its entire length under it and parallel with it. These are called locking bars; for, being moved to the right or left by the action of the levers they hold these levers in certain designated positions, nor do they permit them to occupy any other. In this way what is termed the interlocking is effected. The apparatus, though complicated, is simplicity itself compared with a clock or a locomotive. The complication, also, such as it is, arises from the fact that each situation is a problem by itself, and as such has to be studied out and provided for separately. This, however, is a difficulty affecting the manufacturer rather than the operator. To the latter the apparatus presents no difficulty which a fairly intelligent mechanic cannot easily master; while for the former the highly complicated nature of the problem may, perhaps, best be inferred from the example given by Mr. Barry, the simplest that can offer, that of an ordinary junction where a double-track branch-road connects with

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its double-track main line. There would in this case be of necessity two switch levers and four signal levers, which would admit of sixty-four possible combinations. "The signal might be arranged in any of sixteen ways, and the points might occupy any of four positions, irrespective of the position of the signals. Of the sixty-four combinations thus possible only thirteen are safe, and the rest are such as might lure an engine-driver into danger."

Originally the locking bar was worked through the direct action of certain locks, as they were called, between which the levers when moved played to and fro. These locks were mere bars or plates of iron, some with inclined sides, and others with sides indented or notched. At one end they were secured on a pivot to a fixed bar opposite to and parallel with the movable locking bar, while their other ends were made fast to the locking bar; whence it necessarily followed that, as certain of the levers were pushed to and fro between them, the action of these levers on the inclined sides of the locks could by a skilful combination be made to throw other levers into the notches and indentations of other locks, thus securing them in certain positions, and making it impossible for them to be in any other positions.

The apparatus which has been described, though a great improvement on anything which had preceded it, was still but a clumsy affair, and naturally

THE SPRING CATCH-ROD. 191

the friction of the levers on the locks was so great that they soon became worn, and when worn they could not be relied upon to move the switch-points with the necessary accuracy. The new appliance of safety bad, therefore, as is often the case, introduced a new and very considerable danger of its own. The signals and switches, it was true, could no longer disagree, but the points themselves were sometimes not properly set, or, owing to the great exertion required to work it, the interlocking gear was strained. This difficulty resulted in the next and last improvement, which was a genuine triumph of mechanical ingenuity. To insure the proper length of stroke being made in moving the lever—that is to make it certain in each case that the switch points were brought into exactly the proper position—two notches were provided in the slot, or quadrant, as it is called, in which the lever moved, and, when it was thrown squarely home, and not until then, a spring catch caught in one or other of these notches. This spring was worked by a clasp at the handle of the lever, and the whole was called the spring catch-rod. By a singularly ingenious contrivance, the process of interlocking was transferred from the action of the levers and the keys to these spring catch-rods, which were made to work upon each other, and thus to become the medium through which the whole process is effected. The result of this improvement was that, as the switchman cannot move any lever until the spring 

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catch rod is fastened, except for a particular movement, he cannot, do what he will, even begin any other movement than that one, as the levers cannot be started. On the other hand, it may be said that, by means of this improvement, the mere "intention of the signal-man to move any lever, expressed by his grasping the lever and so raising the spring catch-rod, independently of his putting his intention in force, actuates all the necessary locking.*"

* In regard to the interlocking system as then in use in England, Captain Tyler in his report as head of the railway inspecting department of the Board of Trade, used the following language in his report on the accidents during 1870. "When the apparatus is properly constructed and efficiently maintained, the signalman cannot make a mistake in the working of his points and signals which shall lead to accident or collision, except only by first lowering his signal and switching his train forward, then putting up his signal again as it approaches, and altering the points as the driver comes up to, or while he is passing over them. Such a mistake was actually made in one of the cases above quoted. It is, of course, impossible to provide completely for cases of this description; but the locking apparatus, as now applied, is already of enormous value in preventing accidents; and it will have a still greater effect on the general safety of railway travelling as it becomes more extensively applied on the older lines. Without it, a signalman in constantly working points and signals is almost certain sooner or later to make a mistake, and to cause an accident of a more or less serious character; and it is inexcusable in any railway company to allow its mail or express trains to run at high speed through facing points which are not interlocked efficiently with the signals, by which alone the engine-drivers in approaching them can be guided. There is however, very much yet to be effected in different parts of the country in this respect. And it is worth while to record here, in illustration of the difficulties that are sometimes met with by the inspecting officers, that the Midland Railway Company formally protested in June, 1866, against being compelled to apply such apparatus before receiving sanction for the opening of new lines of railway. They stated that in complying with the requirements in this respect of the Board of Trade, they 'were acting in direct opposition to their own convictions, and they must, so far as lay in their power, decline the responsibility of the locking system.' "

To still further perfect the appliance a simple mechanism has since 1870 been attached to the rod actuating the switch-bolt, which prevents the signal-man from shifting the switch under a passing train in the manner suggested by Captain Tyler in the above extract. In fact it is no exaggeration to say that the interlocking system has now been so studied, and every possible contingency so thoroughly provided for, that in using it accidents can only occur through a willful intention to bring them about. 

DOES IT WORK? 193

In spite of any theoretical or fanciful objections which may be urged against it, this appliance will be found an indispensable adjunct to any really heavy junction or terminal train movement. For the elevated railroads of New York, for instance, its early adoption proved a necessity. As for questions of temperature, climate, etc., as affecting the long connecting rods and wires which are an essential part of the system, objections based upon them are purely imaginary. Difficulties from this source were long since met and overcome by very simple compensating arrangements, and in practice occasion no inconvenience. That rods may break, and that wires are at all times liable to get out of gear, every one knows; and yet this fact is urged as a novel objection to each new mechanical improvement. That a broken or disordered apparatus will always occasion a serious disturbance to any heavy train movement, may also be admitted. The fact none the less remains that in practice, and daily subjected through long periods of time to incomparably the heaviest train movement known to railroad experience, the rods of the interlocking apparatus do not break, nor do it's wires get out of 

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gear; while by means of it, and of it alone, this train movement goes unceasingly on never knowing any serious disturbance.*

It is not, however, alone in connection with terminal stations and junctions that the interlocking apparatus is of value. It is also the scientific substitute for the law or regulation compelling trains to stop as a measure of precaution when they approach grade-crossings or draw-bridges. It is difficult indeed to pass from the consideration of this fine result of science and to speak with patience of the existing American substitute for it. If the former is a feature in the block system, the latter is a signal example of the block-head system. As a device to avoid danger it is a standing disgrace to American ingenuity; and, fortunately, as stopping is compatible only with a very light traffic, so soon. as the passage of trains becomes incessant a substitute for it has got to be devised. In this country,

* "As an instance of the possibility of preventing the mistakes so often made by signal men with conflicting signals or with facing points I have shown the traffic for a single day, and at certain hours of that day, at the Cannon Street station of the South Eastern Railway, already referred to as one of the no-accident lines of the year. The traffic of that station, with trains continually crossing one another, by daylight and in darkness, in fog or in sunshine, amounts to more than 130 trains in three hours in the morning, and a similar number in the evening; and, altogether, to 652 trains, conveying more than 35,000 passengers in the day as a winter, or 40,000 passengers a day as a summer average. It is probably not too much to say, that without the signal and point arrangements which have there been supplied, and the system of interlocking which has there been so carefully carried out, the signalmen could not carry on their duties for one hour without accident." Captain Tyler's report on accidents for 1870, p. 35.

SWING-BRIDGES AND GRADE-CROSSINGS. 195

as in England, that substitute will be found in the interlocking apparatus. By means of it the draw-bridge, for instance, can be so connected with the danger signals-which may, if desired, be gates closing across the railroad tracks-that the one cannot be opened except by closing the other. This is the method adopted in Great Britain not only at draws in bridges, but frequently also in the case of gates at level road crossings. It has already been noticed that in Great Britain accidents at draws in bridges seem to be unknown. Certainly not one has been reported during the last nine years. The security afforded in this case by interlocking would, indeed, seem to be absolute; as, if the apparatus is out of order, either the gates or the bridge would be closed, and could not be opened until it was repaired. So also as respects the grade-crossing of one railroad by another. Bringing all trains to a complete stop when approaching these crossings is a precaution quite generally observed in America, either as a matter of statute law or running regulation; and yet during the six years 1873-8 no less than 104 collisions were reported at these crossings. In Great Britain during the nine years I870-8 but nine cases of accidents of this description were reported, and in both the years 1877 and 1878 under the head of "Accidents or Collisions on Level Crossings of Railways," the chief inspector of the Board of Trade tersely stated that,—" No accident was inquired into under this

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head.* "The interlocking system there affords the most perfect protection which can be devised against a most dangerous practice in railroad construction to which Americans are almost recklessly addicted. It is, also, matter of daily experience that the interlocking system does afford a perfect practical safeguard in this case. Every junction of a branch with a double track road involves a grade-crossing, and a grade-crossing of the most dangerous character. On the Metropolitan Elevated railroad of New York, at 53d street, there is one of these junctions, where, all day long, trains are crossing at grade at the rate of some twenty miles an hour. These trains never stop, except when signalled so to do. The interlocking apparatus, however, makes it impossible that one track should be open except when the other is closed. An accident, therefore, can happen only through the willful carelessness of the engineer in charge of a train;—and in the face of willful carelessness laws are of no more avail than signals. If a man in control of a locomotive wishes to bring on a collision he can always do it.

* "As affecting the safe working of railways, the level crossing of one railway by another is a matter of very serious import. Even when signalled on the most approved principles, they are a source of danger, and, if possible, should always be avoided. At junctions of branch or other railways the practice has been adopted by some companies in special cases, to carry the off line under or over the main line by a bridge. This course should generally be adopted in the case of railways on which the traffic is large, and more expressly where express and fast trains are run." Report on Accidents on Railways of the United Kingdom during 1877,.P. 35.

 

GIVE SCIENCE A CHANCE! 197

Unless he wishes to, however, the interlocking apparatus not only can prevent him from so doing, but as a matter of fact always does. The same rule which holds good at junctions would hold good at level crossings. There is no essential difference between the two. By means of the interlocking apparatus the crossing can be so blocked at any desired distance from it in such a way that when one track is open the other must be closed;—unless, indeed, the apparatus is out of order, and then both would be closed. The precaution in this case, also, is absolute. Unlike the rule as to stopping, it does not depend on the caution or judgment of individuals;—there are the signals and the obstructions, and if they are not displayed on one road they are on the other. So superior is this apparatus in every respect—as regards safety as well as convenience—to the precaution of coming to a stop, that, as an inducement to introduce an almost perfect scientific appliance, it would be very desirable that states like Massachusetts and Connecticut compelling the stop, should except from the operation of the law all draw-bridges or grade-crossings at which suitable interlocking apparatus is provided. Surely it is not unreasonable that in this case science should have a chance to assert itself.

In any event, however, the general introduction of the interlocking apparatus into the American railroad system may be regarded as a mere question of the value of land and concentration of traffic. So long as every road terminating in our larger cities 

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indulges, at whatever unnecessary cost to its stockholders, in independent station buildings far removed from business centres, the train movement can most economically be conducted as it now is. The expense of the interlocking apparatus is avoided by the very simple process of incurring the many fold heavier expense of several station buildings and vast disconnected station grounds. If, however, in the city of Boston, for instance, the time should come when the financial and engineering audacity of the great English companies shall be imitated,—when some leading railroad company shall fix its central passenger station on Tremont street opposite the head of Court street, just as in London the South Eastern established itself on Cannon street, and then this company carrying its road from Pemberton Square by a tunnel under Beacon Hill and the Statehouse should at the crossing of the Charles radiate out so as to afford all other roads an access for their trains to the same terminal point, thus concentrating there the whole daily movement of that busy population which makes of Boston its daily counting-room and market-place,—then, when this is attempted, the time will have come for utilizing to its utmost capacity every available inch of space to render possible the incessant passage of trains. Then also will it at last be realized that it is far cheaper to use a costly and intricate apparatus which enables two companies to be run into one convenient station, than it is to build a separate station, even at an in. convenient point, to accommodate each company.


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