200 Years of Rail Communications
September 27 marks the 200th anniversary of public rail transport. Over the course of two centuries since the opening of the Stockton Darlington line, the world’s first commercial route, communications have been essential for rail safety. In this blog, we’re taking a look at how railway communications have evolved over time.
1825: Flagmen on Horseback
The Stockton Darlington line opened on the September 27, 1825, hauling coal by steam locomotives and passengers in horse-drawn carriages.
Just a single, mixed-use line was created with regular passing points to allow for two-way traffic and overtaking. Warnings were therefore essential for safety. However, the most advanced communication system in use for the first eight years of the line was a man on horseback preceding trains.
1825 to 1839: Timetable Operation
On October 10, 1825, the Stockton and Darlington Railway introduced a timetable to maximize usage of the mixed-use line and minimize the time waiting in the passing points.
This system was crucial for safety on a single-line route. In 1839 the timetables were rolled out nationwide in the UK by George Bradshaw. This led to the invention of GMT as a way to standardize time and is, therefore, a direct ancestor of today’s resilient PNT.
1830s and 40s: Bobbies
By the 1830s, the railways were being built around the world. The first American steam train service, the Baltimore and Ohio Railroad, opened in May 1830. The South Carolina Canal and Rail Road Company opened that same year.
Greater use of railways meant increased risks. To prevent collisions, many companies stationed flagmen along the track, acting as human signals relaying warnings via flags or lanterns. In the UK, this was done by hired policemen called Bobbies.
This was the start of more formal signaling systems.
1841 Semaphore
Despite being invented in 1792 by the French Engineer Claude Chappe, semaphore wasn’t used on the railways until 1841, with a version adapted by Sir Charles Hutton Gregory from the maritime and military system.
This innovation was the first to give train drivers unambiguous instructions that could be read at distance.
1840s: Telegraph
Invented independently by both Samuel Morse; and Sir Charles Wheatstone/William Fothergill Cooke in 1837, the telegraph was quickly adopted by rail companies to allow long-distance near-instant communications between signal boxes.
This automated a significant part of signaling and, for the first time, gave true confirmation that a section of track was clear before another train was allowed through. It was a decisive step beyond flags and timetables, laying the foundations for the block signaling systems that would soon follow.
Manual signals were still used alongside the telegraph, with paraffin lamps and colored filters conveying clear instructions to drivers at night.
1850s–1860s: Block Signaling
With the telegraph established, railways moved to block signaling, dividing the line into sections that could only contain one train at a time. Signalers communicated by telegraph to confirm when a train had cleared a block before another was allowed in, automating separation and reducing reliance on human judgement. This principle of controlled blocks became the backbone of railway safety, which is still used in today’s traffic management systems.
1870s: Track Circuits
Invented by William Robinson in 1872, track circuits use the rails themselves to detect the presence of a train. These allowed signals to change automatically to red when a section was occupied, providing a real-time, fail-safe confirmation of train positions. This marked the start of the automated control systems.
1920s: Electric and Color-Light Signals
By the 1920s, electric signaling began to replace oil lamps and mechanical semaphores. Color-light signals gave drivers clear, instant instructions which were visible day and night.
Linked to track circuits, these signals could operate automatically, reducing human error and allowing trains to run closer together safely.
1920s–1930s: Centralized Traffic Control and Interlocking
Centralized Traffic Control (CTC) was first used in the United States, with large-scale installations on the New York Central Railroad allowing a single operator to manage long stretches of track safely. Interlocking ensured that points and signals could only be set in compatible combinations, preventing conflicting movements and reducing human error.
By the 1930s, similar systems were being trialed and rolled out in the UK on busy main lines, and across Europe, Japan, and Australia. These early centralized and interlocked controls laid the foundation for the safe, high-capacity railway networks that would expand worldwide in the coming decades.
1950s: Automatic Warning and Train Protection
Following the UK Harrow and Wealdstone rail crash of 1952, in which three trains crashed as a result of missed signals and 112 people were killed, automatic warning systems began to be implemented. These were rolled out nationally in the UK by the late 1950s and then around the world.
The technology used two magnets placed on the rails before signals (an always-on baseline and a switchable alert to signal danger) that communicated with the cab via a magnetic field sensor on the leading axle that initiated both audible and visual driver warnings.
Failure to acknowledge an alert resulted in brakes being automatically applied – adding a crucial fail-safe.
1990s and 2000s: GSM-R and ETCS/PTC
The rise of mobile technologies allowed rail communications to switch to digital communication standards, with the rail-specific version of the 2G standard, GSM-R, implemented alongside the European Train Control System (ETCS). In the US, Positive Train Compliance is used in their place and was first federally mandated by the 2008 Rail Safety Improvement Act.
GSM-R provides secure, real-time voice and data links between trains and control centers, replacing older analog radio systems, while ETCS allows continuous, in-cab train supervision, enforcing speed limits and signal compliance automatically. PTC effectively does the same, but using GPS, radio, and onboard computers rather than GPS.
Together, these systems enable interoperable, high-capacity operations across national borders, and reduce reliance on line-side signals, enabling trains to operate safely at higher densities.
Today
GSM-R is based on 2G communications and approaches will be obsolete by 2030, with the Future Railway Mobile Communication System (FRMCS) set to replace it.
FRMCS is based on 5G NR technology and will provide high-capacity, low-latency communications for advanced train control, real-time data exchange, and digital signaling systems like ETCS.
In December 2024, a €13.5 million ($15.8 M) MORANE-2 project was launched to validate FRMCS, with funding from Europe’s Rail (EU-RAIL) and the European Smart Networks and Services Joint Undertakings (SNS JUs). This initiative involves a consortium of railway operators, infrastructure managers, and technology suppliers. VIAVI is proving industry-leading test and validation systems to the project.
The project aims to test FRMCS specifications and demonstrate its integration into the European Rail Traffic Management System (ERTMS), paving the way for its deployment across Europe.
VIAVI Technology for Rail
To find out how VIAVI’s test and measurement technologies are used to enable safer rail communications please, check out our railway and mission critical product pages.
Find out our involvement in the FRMCS and the MORANE-2 project – including how our EVOIA Drive Test and EVOIA Assure systems will be used to troubleshoot and undertake network quality assessments – here.
