What happens if a train breaks down on the tracks, has to be reversed or a sudden speed restriction needs to be imposed on the tracks? The future radio-network-based ETCS level 2 system will add new layers of technical safety to situations such as these. Four practical examples illustrate how more accurate data and automated control can help prevent hazardous situations and mitigate the consequences of human error.
Finland’s train control will undergo a thorough overhaul in the coming years. In the Digirail project, the current train control system will be replaced by the European Train Control System (ETCS). The key objectives of the reform are to make rail traffic safer and more reliable.
“Rail transportation is already safe today, and that safety is based on several complementary layers of protection. “ETCS does not change this basic concept, but rather adds new ways to prevent hazardous situations and mitigate the consequences of human error,” says Niklas Lindfors, Development manager for ETCS operations at the Digirail project.
In the radio-network-based ETCS level 2 system, safety-critical information can be continuously transmitted between the train, the track-side safety equipment and the traffic control system. In the current JKV system and ETCS level 1, information is transmitted at individual points along the track and only from the track to the train. At ETCS level 2, the system is able to adapt more quickly to changing situations and to continuous monitoring of the train’s movement. The system can also intervene immediately to halt the train if necessary.
Four practical examples illustrate the kinds of new safety layers that the ETCS can bring to rail transport.
Accurate positioning data helps prevent incidents
If a train breaks down during the trip and can no longer continue under its own power, another train is needed to assist it. In such an emergency situation, one of the most critical pieces of information is the exact position of the train that has broken down.
The ETCS level 2 system provides information on the train’s front-end position and length, so that the position reported by the train operator can be verified against the system’s data. If there is a discrepancy in the data, it can be detected and resolved before the assisting train reaches the broken-down train.
“Accurate and verified positioning data reduces the risk that an assisting train might, based on incorrect data, approach too close to the broken-down train and thus creating, for example, a risk of collision,” says Lindfors.
ETCS determines the train’s permitted reversing distance
Reversing a train is like backing up a car without mirrors or a rear window: the driver cannot see the track behind the train from the cab. That is why it is important to know exactly how far a train can safely reverse. ETCS level 2 adds a new layer of safety: if a train exceeds the safe reversing distance determined for it, the system will stop the train.
Traffic control determines and ensures how far a train can safely reverse, and this information is relayed to the ETCS. Based on the train’s exact position and length, the ETCS will monitor that this limit is not exceeded. If the train reverses too far, the system will initiate emergency braking. In this way, the driver’s actions are complemented by a technical safety layer that helps prevent incidents caused by reversing too far.
Unnecessary waiting at level crossings will be reduced
Currently, the time between when the level crossing is triggered and the train arrives can vary significantly depending on the train’s speed. You may have to wait behind the barriers for a train that is approaching slowly for considerably longer than for one that is approaching quickly.
Long wait times aren’t just a matter of convenience; they can also increase the temptation to take risks and bypass the barriers.
The ETCS level 2 system allows for more precise timing of level crossing warnings based on the train’s positioning data. This way, the waiting time can be kept more consistent regardless of the train’s approach speed. As unnecessary waiting is reduced, the temptation to dangerously bypass the barriers also decreases.
A sudden change in speed restriction can be quickly brought under monitoring
For example, damage or another non-compliance may be detected unexpectedly on the track, requiring trains to slow down rapidly at a specific point. Currently, the train operator is first notified of a temporary speed restriction by traffic control. Until the necessary balises and speed limit signs can be installed along the track, compliance with the speed restriction at the correct location depends on the driver’s knowledge and memory. Installation can take more than a day.
“If, for example, the speed is not reduced in time due to human error, the train’s speed may be too high when approaching a section where the normal operating speed is not safe.” “This can increase the risk of, for example, damage to the rolling stock or, in the worst-case scenario, a derailment,” says Lindfors.
With an ETCS level 2 system, a temporary speed restriction can be electronically incorporated into the train control system within minutes of the need being identified. The system knows where the speed restriction is in effect and what the permitted speed is, and monitors compliance with the restriction. In this way, important safety information is quickly incorporated into automated control, thus reducing the risk that the driver will misinterpret the location of a speed restriction or exceed the speed restriction as a result of human error.
Safety in created in layers
The safety benefits of ETCS level 2 are not based on any single feature, but rather on complementary layers of protection. Nor does ETCS mean that humans would be removed from the chain of safety. On the contrary: the driver, traffic control, safety devices and train control together form a system in which an individual error or misunderstanding will not escalate into a serious incident as easily.
“The ETCS can indeed be thought of as a safety net that is even more dense than before.” “Not all incidents can be prevented, but the system provides additional opportunities to prevent hazardous situations and mitigate their consequences,” says Lindfors.
The Digirail project is making rail transport in Finland safer, smoother and more efficient. The project is reinventing the outdated train control system and introducing a shared European radio-based train control system across the entire rail network. Digirail will enable safe transport, an improved service level and growth of capacity, and it will create a long-term technical foundation for Finnish railway traffic. The Finnish Transport Infrastructure Agency, Fintraffic and the Ministry of Transport and Communications are collaborating in the project with other actors.