Pull out of the fire – Oscar Martos15 July 2014
Fire safety is a critical aspect of railway line and vehicle design. Oscar Martos of the European Railway Agency explains recent regulatory developments.
Since 2008, the following developments have been made relating to fire safety in railways at European level: the introduction of the Technical Specification for Interoperability (TSI), 'Safety in Railway Tunnels'; and the European Standard EN 45545, 'Fire Protection on Rolling Stock - Requirements for fire behaviour of materials and components'.
In railways, interoperability is the ability of a rail system to allow the safe and uninterrupted movement of trains that accomplish the required levels of performance for these lines. TSIs are pieces of European legislation that harmonise those requirements of the rail system to be checked before entering service in order to ensure its interoperability. Once a new TSI is in force, national rules covering the same subject have to be withdrawn.
There are TSIs covering all subsystems (rolling stock, infrastructure and energy) and there are transversal TSIs that set out requirements for several subsystems in order to cover a particular topic - persons with reduced mobility, for example.
The existing tunnel safety TSI
The safety in railway tunnels (SRT) TSI is a transversal TSI that contains requirements for infrastructure, energy, operations and rolling stock in order to cover specific risks to the safety of passengers and on-board staff in tunnels. It also covers risks for people in the neighbourhood of a tunnel where collapse of the structure could have catastrophic consequences.
The risks covered by the TSI are 'hot' incidents - fire, explosion followed by fire, and emission of toxic smoke or gases either in the train or tunnel - and 'cold' incidents such as collision or derailment, and prolonged stops inside a tunnel.
The risks are covered by a set of requirements following the well-known scheme of prevention, mitigation, evacuation and rescue. Preventative requirements include the use in trains and tunnels of materials that are difficult to ignite, specific measures for flammable liquids in trains and monitoring of the train condition before entering in the tunnel. Mitigation requirements are also prescribed, such as fire detection in the technical rooms of the tunnel, fire detection systems, portable extinguishers in trains and a suitable running capability.
Regarding evacuation and rescue requirements, emergency exits are mandated in trains and access to safe areas is mandated in tunnels. Structural requirements for tunnels grant that in the event of fire, the integrity of the tunnel lining shall be maintained for a period of time that is sufficiently long to permit self-rescue, evacuation of passengers and staff, and intervention of the emergency response services. Moreover, in case of immersed tunnels and tunnels that can cause the collapse of important neighbouring structures, the main structure of the tunnel shall withstand the temperature of the fire for a period of time that is sufficient to allow evacuation of the endangered tunnel zones and neighbouring structures.
Firefighting points are required at the portal of the tunnels, or inside the tunnels if the structure is long. In case of fire, trains are required to stop at these firefighting points, and passengers will be evacuated towards an internal safe area or to open air. Firefighting equipment should be provided in these points, readily available for the rescue services.
In addition, an emergency plan shall be prepared detailing: the tasks; the names, addresses and telephone numbers of all relevant organisations; a precise description and plan of the access routes for the rescue services; measures provided; the strategy for evacuation of passengers from the tunnel in the event of an incident; and isolation and earthing procedures.
The revised SRT TSI
In 2011, the SRT TSI entered a revision process in order to extend its scope to the complete European network. Additionally, the revised SRT TSI clarifies the case of very long tunnels with the introduction of internal firefighting points, as well as the operational rules for the circulation of rolling stock in tunnels. All requirements and the method for their assessment have been revised and further harmonised using recent standardisation developments such as EN 45545-2 and EN 50553.
The revised TSI focuses on tunnel requirements. All requirements related to rolling stock have been agreed in the SRT TSI revision process and then integrated into the revised LOC&PAS TSI, which deals with the rolling stock requirements.
The statistics of fire incidents across Europe were used as part of the background information during the revision process. From 2006 to 2009, fire incidents accounted for 3.2% of all incidents, causing 0.3% of all serious injuries and 0.2 % of all fatalities. Only one fatal fire incident occurred in the reporting period, killing nine passengers in 2008.
On average, four people get seriously injured each year by fire incidents on EU railways. These figures apply to old and new rolling stock, and they are not limited to fires in railway tunnels - all rail fire incidents are considered.
The existing SRT TSI requirements have been considered applicable to the intended extended scope; no new TSI requirements have been defined as a consequence of the extended scope.
The scope of the existing SRT TSI is limited to tunnels 1.0-20.0km long; the scope of the revised TSI is applicable to tunnels from 0.1km, with no upper limit.
The revised SRT TSI defines more clearly what a tunnel is: an enclosed part of a line. The length of a tunnel is defined as the length of the fully enclosed section between two portals, measured at rail level.
Where the tunnel can be divided into segments, either by underground stations or other appropriate stopping points, it is the length of these segments that is relevant for the requirements described in the TSI, so one tunnel may consist of more than one segment.
Tunnels of more than 20km, which were not covered by the existing TSI, follow the segmentation concept explained above; thus, no additional safety requirements are needed for these tunnels if they are divided into segments separated by appropriate stopping points that allow swift evacuation.
Having extended the SRT TSI to 'very long tunnels' - considered as a series of segments of 20km (or less) separated by appropriate stopping points - it is necessary to define these appropriate stopping points, which were delineated by firefighting points. A firefighting point is a dedicated stopping point for the train to manage an emergency and rescue in addition to the evacuation.
A survey was carried out in all European tunnels and tunnel projects of more than 20km, and the result was that in most of them, these suitable stopping points are already provided at least every 20km inside the tunnel.
They typically consist of a high-capacity safe area and firefighting equipment for the rescue services to use. This concept has been adopted in the SRT TSI under the name 'internal firefighting points'.
Not all the requirements apply equally to all the TSI-compliant rolling stock. Trains intended for circulation through tunnels of more than 5km have more stringent requirements, especially regarding running capability.
In such trains, it will be demonstrated that braking and traction functions shall not be impacted by a fire to an extent that prevents the rolling stock running at a minimum speed of 80km/h for a duration of 15 minutes. Rolling stock complying with this level of running capability belongs in Category B.
Category A rolling stock is intended for circulation through tunnels of less than 5km, and just has to prove that braking function will not be impacted by a fire for a duration of four minutes.
Freight trains are allowed to circulate through every tunnel with no running capability requirements, although infrastructure managers operating tunnels of more than 20km can demand such trains to be hauled by Category B locomotives.
SRT TSI-compliant Category B trains are deemed to be at least as safe as any other existing vehicle. Therefore, such trains shall be allowed to circulate through the European network without any restriction.
The only exception to this could be the tunnels longer than 20km. Category B trains do not have enough running capability to circulate through a tunnel of more than 20km, because maintaining a speed of 80km/h for 15 minutes covers 20km.
The current TSI does not mandate additional requirements for rolling stock circulating through tunnels longer than 20km as far as these tunnels are specially equipped to be safe for Category B trains.
The revised TSI specifies the requirements to be met by a tunnel longer than 20km to be deemed safe. Internal firefighting points have to be provided in tunnels depending on the length of the tunnel and the category of rolling stock intended to be operated within it in accordance with the table above.
The revised TSI opens the possibility to operate rolling stock of Category A in any tunnels longer than 5km equipped with fire fighting points every 5km.
The material requirements for all rolling stock categories are demonstrated in the revised SRT TSI by showing compliance with the new EN 45545-2. This standard replaces a collection of national rules.
The running capability requirements to be fulfilled by all categories of rolling stock are set out in the new standard EN 50553.
The new TSI foresees two possible solutions for fire-spreading protection measures in Category-B passenger rolling-stock: full cross-sections made of fireproof material designed to contain fire and smoke for at least 15 minutes, or equivalent systems such as water mist.
Water mist systems do not extinguish the fire but contain it for 15 minutes by continuously discharging water on it. They ensure that flame and smoke will not prevent evacuation. Although this system is quite promising, it is still not mature, and the assessment method remains an open point that future TSIs revisions will close this once a harmonised standard is developed.
TSIs generally apply only to new, renewed or upgraded subsystems. Therefore, it is mandatory for new vehicles to meet the requirements of the TSI, and it is mandatory for authorities across the European Union to accept vehicles fulfilling the TSI requirements with no further checks, with two exceptions: the open points and the specific cases.
The open points are requirements of the TSI for which assessment is not harmonised. In such cases, suitable national rules apply.
Specific case status is granted for a member state when the existing conditions of the subsystems within its sphere of responsibility does not - and will not - fulfil the TSIs. In such cases, national rules apply only to the part of the subsystem that is not TSI-compliant.
Last but not least, national rules are allowed to apply in order to check compatibility between a TSI-compliant vehicle and a non-TSI-compliant infrastructure. These national rules must be provided by member states to the European Commission so that it can publish them.
The legal basis for the TSIs is the Interoperability Directive, which regulates the requirements for placing vehicles into service. On the other hand, the safety directive sets out the relevant requirements for the safe operation of the rolling stock, including in terms of operation and maintenance.
This framework brings several advantages: a lot of previously different and often incompatible national rules are harmonised; the remaining necessary national rules for open points, specific cases and compatibility checks are made transparent; a manufacturer can develop a TSI-compliant design that will be accepted across Europe with no additional check ahead of specific cases, open points and compatibility; and railway undertakings may buy such authorised designs with all legal certainty that they will not be rejected across Europe.