Reducing the Risk of Derailments with Improved Standards
Rail travel is very safe, and trains very rarely derail.
Seven train derailments occurred in 2017-18, two involving passenger trains, two with empty coaching stock, and three involving freight trains. These in the context of 215,826 freight train movements and 1.71 billion passenger journeys made in that financial year.
There have been no passenger or workforce fatalities from train accidents for over 12 years, since Grayrigg in 2007. But while there were no major injuries to the workforce or passengers from the derailments that occurred in 2017-8, they still have the potential for tragic consequences.
Even derailments without injury are problematic, since they cause considerable delay and disruption to other rail services while the immediate investigation and restoration of order takes place.
While the long-term trend has been for the number of derailments to fall year by year, the freight sector in particular has been keen to reduce the risk even further.
Between 2007 and 2013 there were five derailments on Britain's railways involving container freight trains, due to combinations of track twist, wagon fault and asymmetric or offset loading. The Rail Accident Investigation Branch (RAIB) recommended, after the Camden Road and Gloucester derailments in October 2013, that RSSB should add assessments for a vehicle's resistance to offset loading and to cyclic top track features within the Railway Group Standard (RGS).
The Cross-Industry Freight Derailment Working Group was set up to address the RAIB recommendations. It has been specifying and supporting the implementation of short-, medium- and long-term measures that will reduce the risk of freight derailments so far as is reasonably practicable. One of the agreed measures involves an assessment for ISO container carrying wagons, in three different offset load conditions. This is a new requirement within the RGS.
As part of separate RSSB research, an assessment for susceptibility to cyclic top track features has been developed. This assessment checks that a vehicle has sufficient vertical damping at a range of speeds. This is also a new requirement within the RGS.
All rail vehicles, whether they are for passengers or freight, or a locomotive, need to be able to negotiate the range of track features encountered out on the network. These requirements are set out in TSIs – Technical Specifications for Interoperability. These define the technical and operational standards that all railways across the EU must meet to ensure consistency in safety and the ability for railway operators and the supply chain to operate smoothly across borders.
The LOC&PAS and WAG TSIs refer to European standard BS EN 14363 which describes test procedures and requirements for slow speed flange climb and for 'dynamic behaviour' to ensure a vehicle is fit for purpose, therefore reducing the risk of derailment.
Historically, Britain has had its own RGS, which sets out a different test method and requirements to the ones described in BS EN 14363. RSSB research has confirmed that this test provides equivalent safety to the BS EN 14363 test, and so is a permitted way of complying with BS EN 14363 and the TSIs. This new permission is a key advantage of the updated RGS and will enable significant cost savings to be made for vehicles operating in Great Britain compared to using the core EN process.
The updated RGS, GMRT2141 Issue four, 'Permissible Track Forces and Resistance to Derailment and Roll-Over of Railway Vehicles', was published in June 2019.
There are new requirements for:
- Assessing susceptibility to derailment due to cyclic top and validation of simulation models for the cyclic top assessment
- Testing ISO container-carrying vehicles in offset loaded conditions
There are updated requirements for:
- The selection of on-track ride test routes and conditions.
- Vertical and lateral forces - ramp / kink angles reduced for high speed (above 100 / 110 mph)
- Roll-over due to overspeed: reduced to 18° for non-tilting passenger vehicles, and a clarification that On-Track Machines have the same requirement as freight vehicles
- The wheel load to wheel diameter (Q/D) limit - increased from 0.13 to 0.17 (for wheel diameters of 460 mm or above)
There are some withdrawn documents:
- GMRT2141 Issue four now absorbs the National Technical Rules from GMTT0088 issue one and its associated code of practice, GMRC2513, both of which have been withdrawn.
The updated RGS means that Great Britain is now leading the way in 'safety against derailment'. The cyclic top and offset load assessments are not yet part of the BS EN 14363 requirements. The GB delegates are currently working with the European working groups to consider adding these assessments to future updates of the EN.
GMRT2141 issue four applies to all new designs of rail vehicle introduced to market and put into service on Britain's railways.