Railroad signals are used to communicate important information to train operators about the status and condition of the track ahead. These signals are an essential part of the railway system, helping to improve safety and efficiency on the tracks.
There are several different types of signals that can be used on a railroad, each with its own specific purpose and method of operation. One common type of signal is the fixed block signal, which is a stationary signal that is mounted on a pole or other support structure along the track. These signals use a series of colored lights, such as red, yellow, and green, to indicate the status of the track. Red usually indicates that the track is occupied or not clear, while green indicates that the track is clear and a train can proceed. Yellow signals are used as a cautionary indication, warning the train operator to be prepared to stop if necessary.
Fixed block signals are typically used in conjunction with other types of signaling equipment, such as track circuits and occupancy detectors. Track circuits are electrical circuits that are used to detect the presence of a train on a particular section of track. These circuits use a battery and a relay to detect the presence of a train and control the movement of trains through the use of block signals. Occupancy detectors are sensors that are used to detect the presence of a train on a particular section of track. These sensors can be either physical or electronic, and are used to provide an additional level of safety by helping to ensure that the track is clear before a train is allowed to proceed.
Another type of signal that is used on the railway is the cab signal, which is a mobile signal that is mounted inside the locomotive cab. These signals use a series of lights or other indicators to inform the train operator of the status of the track ahead. Cab signals are often used in conjunction with fixed block signals, and are particularly useful in areas where the track layout or terrain makes it difficult to see the fixed block signals.
In addition to wayside signals, there are also other types of signals that are used on the railway, such as interlocking signals and crossing signals. Interlocking signals are used to control the movement of trains at points where multiple tracks intersect, while crossing signals are used to alert drivers of vehicles on the road that a train is approaching a grade crossing.
Overall, the design and operation of railway signals, including communication and signaling systems, must consider various factors such as track layout, terrain, and train traffic. It is important to follow recommended practices, such as those outlined in the AREMA Communications and Signals Manual, to ensure the safe and efficient operation of railway signals.