At first there were three. Well, actually five. Now there are two. Well, more like four. The confusion around Europe’s standardised signalling safety system ERTMS extends far beyond this particular problem, but one key question that keeps on popping up is whatever happened to ERTMS/ETCS Level 3? RailTech breaks it down, along with all the other questions about ERTMS you might have been too embarrassed to ask.
To give a brief overview for the uninitiated, the European Rail Traffic Management System (ERTMS), is a standardised signalling and train control system designed to enhance safety, interoperability, and efficiency across Europe’s railway networks. It allows for seamless communication between trains and trackside infrastructure using unified technology, and it means that various networks don’t have to change signalling systems when crossing borders.
It also features Automatic Train Protection (ATP), so if a train exceeds speed limits, approaches a stop signal, or risks collision, ATP automatically puts on the brakes. At certain levels, it also removes the need for trackside signalling equipment, and because it integrates with Automatic Train Operation (ATO), it also paves the way for semi- or fully autonomous train systems in the future. The EU’s executive has been pushing the system since the 1990s in a bid to better integrate the bloc’s train networks.
What’s the difference between ERTMS and ETCS?
Often confused, ERTMS is the overarching system for standardising rail signalling, while ETCS (European Train Control System) is a core component of ERTMS, specifically focused on train control and safety functionalities. While ERTMS includes broader elements like GSM-R for communication and system-wide interoperability, ETCS specifically governs onboard and trackside interactions to manage train speeds, signals, and braking.
Essentially, ERTMS is the brain coordinating the train systems, while ETCS is the hand on the controls, ensuring each train moves safely and smoothly.
How many levels of ERTMS/ETCS are there and what do they mean?
Currently, there are four ERTMS/ETCS levels: L0, LNTC, L1, and L2. As ERTMS.net explains, the different ERTMS/ETCS application levels are a way to express the possible operating relationships between track and train. Level definitions are essentially related to the type of trackside equipment used, the way trackside information reaches the trains, and which functions are processed trackside and onboard.
While we talk about ERTMS levels, we’re essentially talking about the different uses of ETCS as a train control system.
Level 0 is for trains running on tracks that don’t have ERTMS equipment. The trains rely on existing signals or systems already in place, and ERTMS doesn’t control them. It’s like driving a car on roads with no traffic lights or signs, where the driver is responsible for everything.
With Level NTC, short for National Train Control, ERTMS acts as a helper when a train operates on tracks using older, national signalling systems. The train’s ERTMS equipment connects with the existing system, ensuring it can follow local rules safely. Think of it as using a GPS app that adapts to local road laws when driving in another country.
What’s the difference between Level 1 and Level 2?
But the main levels essentially start with ERTMS Level 1. Level 1 adds ERTMS technology to tracks that already have traditional signals and train detectors. It uses devices called balises placed on the tracks to send information to the train about speed limits, braking points, and signals ahead.
The onboard system helps the driver by automatically calculating safe speeds and braking if necessary, improving safety without replacing the entire infrastructure. It’s like adding smart road signs and automatic braking to older highways. It’s a cost-effective way to upgrade safety and interoperability without completely replacing the existing infrastructure.
The key difference between Level 1 and Level 2, is that the latter removes the need for the trackside signals by using a wireless system to communicate directly with the train. A central hub, called the Radio Block Centre (RBC), sends continuous updates about the train’s speed, location, and what’s ahead.
So there’s no trackside equipment?
Essentially, Level 2 uses a wireless system (via GSM-R/FRMCS radio) to send important information directly from an RBC to the train. However, while this setup reduces the need for physical signals along the tracks, the system still relies on trackside equipment to detect where trains are and confirm they’re intact.
The train’s onboard computer works alongside this, continuously checking its position and speed using special devices on the tracks, called passive balises, and information from the RBC. This allows the system to give the driver real-time updates about speed limits, signals, and what’s ahead, ensuring the train can travel at its best speed while staying safe. Compared to Level 1, Level 2 cuts costs by making traditional signals optional and increases efficiency by allowing trains to run closer together at higher speeds, which means smoother and faster service for passengers.
To get an idea of what it really means to implement these two different systems, check out our article on the problems faced in the Netherlands by trying to exclusively roll out ERTMS Level 2 all at once. Spoiler alert: they didn’t manage to do it, and it set back the rollout by several years.
So what’s Level 3 then?
ERTMS/ETCS Level 3 was originally conceptualised in the early 1990s as part of the EU’s most early initiative to standardise railway signalling and control systems across member states. The main difference between Level 3 and Level 2 at the time was in the difference between train detection and integrity supervision.
In Level 2, those functions were managed by trackside equipment, such as track circuits or axle counters, which detect train presence and ensure the train is complete. By that, we mean the entire train—every carriage, wagon, or part that is supposed to be attached—is still intact and connected. That’s crucial because if any part of the train becomes detached, it could cause accidents or block the tracks.
Conversely, Level 3 shifts these responsibilities to the train itself, utilising onboard systems to report its position and “completeness” directly to the Radio Block Centre. That allows for more accurate train location data and enables the use of moving block systems. They dynamically manage the safe distance between trains based on their real-time location and speed, rather than relying on fixed sections of the track.
But what happened to Level 3?
To get to the point, Level 3 hasn’t disappeared; it’s simply been merged into another level. Level 3 was combined with Level 2 last year under updated regulations (CCS TSI 2023). This means Level 3 is no longer treated as a separate system, and its features, like more flexible train spacing and onboard monitoring of train integrity and location, are now fully included in Level 2, which is already being rolled out across much of the EU.
Imagine Level 2 as a car with cruise control that uses sensors along the road to stay safe, and Level 3 as a car with advanced self-driving that doesn’t rely on road sensors but instead uses its own onboard tech to monitor everything. Now, with the merging, Level 2 has been upgraded to include the self-driving features of Level 3, so there’s no need to call them two separate systems – it’s all just one smarter car.
This article was originally published on our sister publication RailTech.com.