Verenigde Staten





Het boek "Elements of Railway Signalling", GRS, Pamphlet 1979 uit juni 1979, beschrijft in het hoofdstuk "A Brief history of railway signaling" de geschiedenis van het seinwezen in de VS (tot 1979 uiteraard) grotendeels aan de hand van eigen producten en projecten als volgt:

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Although the date of 1814 is given as the first practical use of George Stephenson’s invention, the steam locomotive, signaling is even older. The first rail cars were pulled by horses or mules and were used in mines and quarries. Records as early as 1806 show that hand and arm signals were used to direct the drivers of these early “trains”. Hand signals, flags - and at night, lanterns - were used to signal B & O trains in 1829. In some instances, a mounted flagman preceded the train - indeed this custom continued in New York City, on West St., as late as the twenties. Signaling using fixed wayside signals probably first began, in the United States, on the New Castle and Frenchtown R.R., in 1832. This 17-mile long railroad, connecting New Castle, Delaware with Frenchtown, Maryland, used fixed signals, flags at first and later ball signals, to pass information from one terminal to another.

BLOCK SIGNALING
In the early days of railroading, trains were operated (more or less) by schedules. Thus train separation was a time separation. As traffic increased, tracks were divided into blocks, and train separation was by space interval. Thus block signaling began. Various electrical and mechanical systems were tried. Basically, they were designed to let one train pass into a block and to inhibit the block entering signal from clearing to allow another train into the block until the first train was reported to have left the block. Later systems added a permissive feature, allowing trains to follow each other into the same block
Beginning in 1851, the electric telegraph was used to determine the locations and progress of trains along the line and to transmit train orders to expedite traffic.
These systems all required substantial manpower and had no protection against a part of a train being accidentally left in a block between signal stations.
August 20, 1872, marked one of the most important events in railway signaling, the invention of the closed track circuit by Dr. William Robinson. First installed at Kinzua, Pa. on the Philadelphia and Erie R.R., the closed track circuit soon proved its worth, and other installations followed rapidly. All modern track circuits are based on Dr. Robinson’s original concept, even though their capabilities have been greatly amplified by modern track relays, coding, and more recently, electronic techniques such as the GRS high-frequency jointless track circuits.
The next great advance in the block signaling area of railway signaling came in 1911, when a GRS engineer, Sedgwick N. Wight, invented absolute permissive block signaling. This system, now called APB, allows trains to operate in either direction on single track with full signal protection for both following and opposing movements. A later GRS development, Trakode, provides APB signaling without the use of signal-control line wires.

INTERLOCKING
The first installation resembling interlocking was installed in England, in 1843, at a place called Bricklayer’s Arms Junction. The switches and signals were operated by a switchman. Connections to the field were via pipe and wire pull. There were hand levers operate the switches and foot stirrups to work the signals. There was no interlocking among the switches and signals. Switches were sometimes thrown under trains and signals cleared over open switches, but the advantages of centralizing control were achieved.
Various arrangements were soon devised to prevent the operation of occupied switches and then to interlock the switch and signal controls. However, it wasn’t until 1856 that the first mechanical interlocking appeared that met what we now consider essential interlocking requirements. It was developed in England by John Saxby.
The first interlocking in the United States, a Saxby & Farmer imported from England, was put in service in 1870, at Trenton, N.J., on the property of the United New Jersey Canal and Railroad Companies. Many more mechanical interlockings were installed, and numerous improvements were made to the system. American manufacturers, GRS among them, produced the bulk of mechanical interlockings in the U.S. until they were gradually superseded by various types of power interlockings, interlockings which did not depend on human muscle power to throw the switches and set the signals.
Several power interlocking arrangements were tried, such as hydropneumatic and electro-pneumatic systems, which proved the advantages of power operation but suffered from various disadvantages. Then, in 1901, the Taylor Signal Co., one of the predecessors of GRS, put in service the first all-electric, dynamic indication interlocking, at Eau Claire, Wis., on the Chicago, St. Paul, Minneapolis and Omaha Railway. This system was unique in that it proved the operations of the switches and signals by requiring reception of a “dynamic indication” current back at the control tower to operate the locking latches in the levers. The dynamic indication current was generated by the free spin of the armature in the electric motor in the semaphore signal and in the electric switch machine as they completed their movement to a called-for position. This system was an immediate success, and thousands of levers were installed, some of which are still in service.
The next development, relay interlocking, which requires no mechanical locking between the levers, developed with centralized traffic control.

CENTRALIZED TRAFFIC CONTROL
On July 25, 1927, the first centralized traffic control system in the world went in service between Stanley and Berwick, Ohio, on the Ohio Division of the New York Central Railroad. This system, invented by the same Sedgwick N. Wight of the General Railway Signal Company who had earlier invented APB, was a tremendous stride forward in improving facility and economy of train operation.
Here is a first-hand account of operation with the new system as given in an address by Mr. J. J. Brink- worth of the New York Central Railroad before the Signal Section of the Association of American Railroads in 1947.

“. . . . I was particularly involved in centralized traffic control in 1927. I went to Rochester, to the General Railway Signal Company plant, and saw the actual machine there. I, of course, became acquainted with Mr. S. N. Wight of that Company, who studied out the details of the cTc machine. I went to his house and in the back room we talked it over in detail for hours.
Then we came to 1927, when the final date was set to install centralized traffic control on the Toledo & Ohio Central and put it into service. Needless to say, we were all over at Fostoria, Ohio, and we watched the progress of the various signals being put in along the approximately 40 miles of railroad between Toledo and Berwick. Then, after a comparatively short time, trains started to move over that piece of single track for the first time without train orders.
“I recall very distinctly, as we had supper in the hotel at Fostoria and got through, I said to the gang, I do not know what you fellows are going to do tonight, but I’m going over to the tower at Fostoria and stay there until I see a non-stop meet. Well, they all decided that if the boss was going over, the rest of the gang had better go, too. So we went over to the tower at Fostoria in the evening. The dispatcher was there and he was just filled up with enthusiasm on this new gadget called
centralized traffic control Along about 10:00 o’clock, he just yelled right out loud, “Here comes a non-stop meet’’. Well, we all gathered around the machine and watched the lights that you know all about, watched the lights come towards each other and pass each other without stopping.
“That, to me, and to you, too, was history on American railroads, the first non-stop meet on single track without train orders, of course, that we knew of. We waited at Fostoria until the southbound train arrived there and you never saw such enthusiasm in your life as was in the minds and hearts of that crew, the first non-stop meet of which they had ever heard.’


Thus occurred the first non-stop meet, today commonplace on thousands of miles of cTc.
The beginnings of pushbutton signal systems, this NX interlocking machine (the world’s first) was placed in service at Brunswick, England in 1937.

ALL-RELAY INTERLOCKING
All-relay interlocking was an outgrowth of the principles applied so successfully in centralized traffic control. Now the cumbersome lever locking beds of the electric interlocking machine were abandoned in favor of relay interlocking between the switches and signals in the field. Control distance ceased to be an important factor.
GRS furnished equipment for the first remotely controlled, unit-wire all-relay interlocking system, put in service February 1929, on the Chicago, Burlington and Quincy at Lincoln, Nebraska.

CAR CLASSIFICATION
GRS led the field with the first commercial installation of all-electric car retarders, in 1926, at East St. Louis on the Illinois Central Railroad.
The next significant development in car classification was the invention by GRS, in 1930, of the automatic switching system. The initial installations of this system were made at Markham Yard, Illinois, on the Illinois Central Railroad, and St. Luc Yard, Montreal, on the Canadian Pacific, both in 1930.
In 1933, another GRS invention, automatic retarder control using a GRS analog computer was installed at Kirk Yard, Gary, Indiana, on the Elgin, Joliet & Eastern. This system marked the use, now common, of radar and of computer technology in railway signaling.
on the New York Central in 1937.

AUTOMATIC TRAIN CONTROL
It is doubtful if any special subject ever received as much attention as did automatic train control. Thousands of patents were issued, millions of dollars spent in experimentation, and yet only a few systems have survived the tests of practical use.
A trial installation of GRS intermittent inductive train stop was made on the Buffalo, Rochester and Pittsburgh Railway in 1919. By 1923, the first commercial installation was made on the Chicago and North Western Railway, and many installations followed.
Today, however, the most modern types of train control are used on rapid transit systems, such as the GRS installations at Washington, D.C., Boston, Chicago, and, most recently, Atlanta.

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De ingesloten youtube video van Norfolk Southern toont de ontwikkeling van "Communications and Signals" technology in de Verenigde Staten. vanaf de twintiger jaren, met de introductie van de All Relay technologie zie je veel overeenkomsten met de ontwikkelingen in Nederland na de tweede wereldoorlog. Met de introductie van de computer based signalling zie je de ontwikkelingen weer uit elkaar gaan. Met uitzondering van de VPI interlockings.

Hotbox detectie kennen we in Nederland ook, maar op zeer bescheiden schaal, de andere wayside inspection technologie zie je in Nederland niet, maar wel bijvoorbeeld in Zwitserland bij de ingang van de grote alpen tunnels.

Overwegbeveiliging ziet er weer heel bekend uit voor ons.