An overview of my contribution in the DYNAFREIGHT project in the Shift2Rail initiative.

Background

Robust operation of heavier and longer freight trains is essential to move towards increasing the competitiveness of rail transportation. From a European perspective, this typically means running long freight trains (>800 m). This shorter length for 'long' trains in Europe compared to the rest of the world that routinely operates 2-4 km long trains is due to various factors which was explored extensively in this project. There are technical challenges such as,

• prevalence of traditional pneumatic (P-type) braking systems
• side buffers & screw-coupling systems
• lack of long sidings
• tight curves

Also, from an operational standpoint, it is desirable to have multiple radio-controlled locomotives in long trains that can be controlled by the driver from the lead locomotive. This means it is important to also consider the worst case scenario when communication between locomotives fail or get delayed. Therefore, fail-safe protocols needed to be built into the radio-controlled pneumatic braking system.

.. from an operational standpoint, it is desirable to have multiple radio-controlled locomotives in long trains that can be controlled by the driver from the lead locomotive

In this project, I studied the derailment risks of radio-controlled braking in infrastructure bottlenecks, and guidelines for building long trains with the corresponding tolerable forces respectively.

Derailment risks in infrastructure bottlenecks

Longitudinal Train Dynamics (LTD) and its influence on running safety of freight trains is a key issue when it negotiates tight switch curves. Standards such as the UIC Code 530-2 and EN-15839 detail the procedure for on-track propelling tests that should be conducted to determine the running safety of a single wagon that consider tight S-curves, neighbouring wagons and buffers.

A three-dimensional multi-body simulations-based approach was developed to judge the derailment risk of a train with regards to its longitudinal dynamic behaviour. The derailment risk is expressed as Longitudinal Compressive Force (LCF) limits & Track forces for wagon combinations passing through S-curves of varying curvatures.

The derailment risk is expressed as Longitudinal Compressive Force (LCF) limits & Track forces for wagon combinations passing through S-curves of varying curvatures.

Guidelines for building long freight trains

Long freight trains can have several wagons and multiple locomotives along its length. In addition to braking, the distribution of payload can affect the wagon dynamics and therefore certain combinations need to be avoided. Based on the derailment risks calculated at infrastructure bottlenecks, critical train configurations and braking scenarios were identified and tested on track. It consisted of:

• empty wagons placed between loaded wagons
• Flat wagons with low torsional flexibility placed in between rigid and shorter coal wagons
• emergency braking protocol when radio communication between locomotives fail

The test with mixed train configuration with three locomotives (two remotely controlled) was carried out in 2021 in Germany to demonstrate the feasibility to operate radio-controlled long freight trains.

critical train configurations and braking scenarios were identified and tested on track

More detailed description of the project, methodologies, and tools used can be found in the references below.

Distributed Power System demonstrator with mixed train configuration

References

1. Press release: DPS: Distributed Power System, the way to the long train, DB Cargo.
2. Project report: Deliverable 3.2: Safety precautions in train configuration and brake application.
3. Journal article: Tolerable longitudinal forces for freight trains in tight S-curves using three-dimensional multi-body simulations.
4. Journal article: An integrated numerical framework to investigate the running safety of overlong freight trains.
5. Website: DYNAFREIGHT

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