Traffic lights, traffic signals, or stoplights – also known as robots in South Africa – are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic.
A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal might inform the driver of the speed at which the train may safely proceed or it may instruct the driver to stop.
Railway signalling (BE), also called railroad signaling (AE), is a system used to control the movement of railway traffic. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year.
The signalling system used on the rail transport in Norway is regulated by the Regulations of December 4, 2001 no. 1336 about signals and signs on the state's railway network and connected private tracks.
A motor vehicle has lighting and signaling devices mounted to or integrated into its front, rear, sides, and, in some cases, top. The devices illuminate the road ahead for the driver and increase the vehicle's visibility, allowing other drivers and pedestrians to see its presence, position, size, direction of travel, and its driver's intentions.
The railway signalling system used across the majority of the United Kingdom rail network uses lineside signals to control the movement and speed of trains.
Australian railway signalling varies between the States of Australia, because the individual States are responsible for the railway systems within their own borders, with, historically, no need to co-ordinate between states except at the boundaries.
Railway signals in Germany are regulated by the Eisenbahn-Signalordnung. There are several signalling systems in use, including the traditional H/V (Hauptsignal/Vorsignal) system.
The signalling system used on the standard-gauge railway network in Sweden is based on that of the traditional mechanical semaphore signals. Currently only colour-light signals are used, together with the Ansaldo L10000 Automatic Train Control system.
In traffic engineering, there are regional and national variations in traffic light operation. This may be in the standard traffic light sequence or by the use of special signals.
North American railroad signals generally fall into the category of multi-headed electrically lit units displaying speed-based or weak route signaling. Signals may be of the searchlight, color light, position light, or color position light types, each displaying a variety of aspects which inform the locomotive operator of track conditions so that they may keep their train under control and able to stop short of any obstruction or dangerous condition.
Railway semaphore signal is one of the earliest forms of fixed railway signals. This semaphore system involves signals that display their different indications to train drivers by changing the angle of inclination of a pivoted 'arm'. Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most widely used form of mechanical signal. Designs have altered over the intervening years, and colour light signals have replaced semaphore signals in most countries, but in a few they remain in use.
Japanese railway signals, according to the ministerial decree defining technical standards of railways, are defined as indicating operational conditions for railway staff driving trains.
The Italian railway signalling currently in use, employed on the Italian national railway network, is regulated by the "Regulation on signals", issued by the Italian railway infrastructure manager, RFI.
The first railway signalling in Greece was installed on the Athens–Piraeus Railway at the turn of the 20th century, when semaphores and boards were added with the line's electrification. Other Greek trains at that time were controlled by signals given manually by station masters. During World War II, German occupation forces installed mechanically operated semaphore signals at the entrance to all stations, with some light signals at busy stations. Modern signalling is provided through colour light signals. Radio communication between train stations and drivers was introduced in 1973 and digital communication is an ongoing present-day introduction.
Belgian railway signalling is the signalling in effect on the Belgian rail network currently operated by Infrabel.
The Polish (PKP) railway signalling system provides a complex outlook of traffic situations, yet is quite easy to understand. Signals can be divided into following categories:
Ledbury Signal Box is a typical Great Western Railway traditional lever frame signal box which remains in daily use at Ledbury Station, Herefordshire, England on the railway line from Worcester to Hereford.
Semaphore is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arranged in visually connected networks, or for traffic signalling such as in railway systems, or traffic lights in cities.
The Royal Bavarian State Railways had their own Bavarian railway signals for decades until they were gradually replaced by Deutsche Reichsbahn semaphore signals following the merger of all the German state railways into the newly created Deutsche Reichseisenbahnen in 1920. Bavarian home signals were still being used by the Deutsche Bahn until 2002 and Bavarian distant signals even after that.
