There was a time when railroad switches were directly operated in place by operators, but it was often difficult for them to coordinate effectively their maneuvers. This problem was later solved by means of signal boxes with remote switching operated by a sole operator; to actuate the track switches, even at a distance of three kilometers, it would be enough to manage a number of levers; if the railroad switch does not move, the lever can give a warning to the operator by opposing a certain resistance; in such case it would be indispensable to manually control the railroad switch in place to avoid a disaster. The arrival of more modern switching centers allowed a single person to control a large number of individual track switches by means of small levers and electric panels showing the current status of the railway network, while automatic interlocking systems allow to prevent the human errors in the maneuvers.
First signal boxes for railroad switching.
If otherwise what is required is to transfer a vehicle from a track to another track which runs parallel, it is sometimes used a rotatory platform provided with two track sections disposed in cross. It is not unusual that two trains meet while marching in opposite direction in a single-track line; in such case the train which arrives first must wait in the station, where it will be effectuated the crossing when arriving the second train. It can also happen that two trains meet while moving along the same track in the same direction; then the train which first reaches the station must grant precedence to the second train.
As stated, it is very important the automatization of signals; because of this it is the very train which actuates a signal setting it in stop status towards other trains if necessary. Signaling block systems have the purpose of warranting the safe circulation of trains. The first of these systems was built by British telegraph engineer Fothergill Cooke and installed in 1848 in the line Norwich-Yarmouth of the Great Eastern Railway. These systems are based in the subdivision of a line in many sections by means of signals, so in a particular section between two signals is allowed to be only one train at a same time. If the line has two tracks, each of these have independent sections; in a single track, it is necessary to dispose things in such a way that two trains marching in opposite direction meet each other in a section provided with a crossing track.
Let us see an example of how an operation is made between two nearby signaling block posts, placed in two positions named as A and B. The operator in A, who is awaiting a train, requests to the operator in B to unblock the signal if the line is free, to allow transit to the incoming train; then it could be unblocked the signal and the train could pass. As soon as the train has passed, the operator in A immediately blocks the signal, but even if he does not, the signal will be automatically blocked by the train itself by means of an electric switch placed in the rails. The operator in A has also to inform the operator in B about the train passing, so he can block his own signal, not allowing other train to pass until the first train has actuated the electric switch which automatically unblocks the signal, freeing so the line. This switch would be placed after the signal at a distance equivalent to at least the length of a train, to ensure that when it is actuated the track section is free.
It is easy to imagine the relation existent between signaling block and the invention of the telegraph. In fact railway signaling uses a simplified version of the mentioned communication system, transmitting just a small range of signals such as "busy line" or "free line"; for reading these warnings are used electromagnetic circuits which represent the different signals in panels installed in the signal boxes, small masonry buildings where the operators work in their maneuver benches, from which they control both the railroad signals and switches. Modern railway signals and switches are all or almost all electric or electronic; they are fundamental for the safe circulation of the trains and their automatization is intended to avoid the human error, of fatal consequences.
Railroads in the cities
Already in the 17th century some inventive men had the idea of establishing services for public transport inside the cities or between these and the suburban areas, but given the preference for the use of particular vehicles or stagecoaches, these ideas remained unrealized. In the beginning of the history of the railway, the railroads were used only in the mines and only later they started to be used by passenger cars towed by horses. The public transport properly said appeared in New York in 1832, with the introduction of the first tramcar, towed by horses as well. This line connected the downtown with the suburbs of Harlem. These cars were provided with tug shafts in both ends to allow to reverse the march without requiring the installation of rotatory platforms in the terminals of the line.
Almost 20 years passed before new lines were inaugurated in the city, but meanwhile the cars had increased their capacity by adopting a second story known as "imperial", accessed by stairs on both ends of the car. In England, however, the first tramcars did not appear until circa 1860 and this happened thanks to an American entrepreneur who had to suffer a strong and understandable opposition from the particular coachmen. Also in France, circa 1853, it was inaugurated the first tramcar which connected the Place de la Concorde in Paris and Saint Cloud. Slowly but successively, in all the main cities of Europe and America started to appear the railroads, and in 1870 almost all of them had at least a tramcar towed by horses.
Henry Casebolt built in 1878 this railroad stagecoach for the public transport service in San Francisco. This design with a rotatory body allowed to reverse the direction without having to turn around the wheel truck.
A small wagon fitted with skids, built by Stephenson specially for the temperatures of -40 degrees reached in Manitoba, and a Chinese car from 1880.