I N N O V A T I O N . T E A M W O R K . P E R F O R M A N C E . I N T E G R I T Y .

Fire Safety for Tunnels Tony Pearson Senior Consultant Fire Engineering (Europe), Exova Warringtonfire IFSEC, 16 June 2015

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• The challenge • Approach to fire safety design • Fundamental parameters • Risk control measures

Fire Safety for Tunnels

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Accident rates in tunnels are low, but... • Restricted access/egress • Heat & smoke trapped • Recent experience: fires likely to be larger than previously assumed • “Normal operation” involves challenges, e.g. traffic jams, polluted

atmosphere • Scientific community does not know enough about tunnel fires If something goes wrong, it can go very badly wrong

The Challenge

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Code-based design (“prescriptive approach”) e.g. NFPA 502 (road)/ NFPA 130 (rail)

“if tunnel more than x m long ventilation required”

Engineered design (“performance based approach”)

“imagine a fire – how can we control conditions?”

Approach

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• Common misconception: Code-based = best practice Engineering = cheap solution

• Code-based approach usually delivers a reasonable design Not necessarily the best possible design

• Engineering approach may produce better solution “Outputs” only as good as “inputs”

If underlying assumptions inappropriate, resulting design may be very bad

Approach

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• Whichever approach taken: Fire safety should not be a “bolt on” to the design, should be ingrained in design

Approach

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• Road or rail Impact on – Likelihood of an incident – Likely casualty numbers – Access – Ventilation – Air quality – Staffing concept

• Length – Access/egress – Ventilation

• Incline – Ventilation – Fire service access

• Traffic volume – Access – Ventilation – Staffing concept

Step 1: Fundamental Parameters

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• Location – distance from towns, geology, under water? – Access/egress – Ventilation

• Number of bores – Ventilation concept – Access/egress concept

• Pollution-control needs – Ventilation

Step 1: Fundamental Parameters

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Order of priority • Prevent incidents • Detect incidents • Limit extent of fire • Means of escape • Intervention • Reliance on human behaviour

Hierarchy of Control Measures

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• Channel Tunnel, 1996: lorry was on fire before it entered tunnel Kaprun funicular, 2000: train was on fire before it entered the tunnel → Traffic management, CCTV etc to identify burning vehicles and

stop them before they enter tunnel • Traffic restrictions

Speed limits, prohibition of dangerous goods etc

Prevention

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• Use combination of systems, e.g. – heat detector – flame detectors – CCTV – automatic image recognition – CO monitors

Detection

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• Use combination of systems, e.g. – heat detector – semiconductor sensors, fibre-optic, hollow-tube... – flame detectors – UV, IR – CCTV – automatic image recognition – CO monitors

• Difficulties: – localising fire on moving vehicle – detection in polluted environment

Detection

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Ventilation • Aim: extract heat and smoke without fanning fire • Up to approx. 500 m: natural ventilation may be viable • Twin-bore – common concept: blow smoke in direction of travel

(“longitudinal ventilation”) • Single-bore – “transversal” or combination transversal/longitudinal

– extract smoke to protect escape routes – restrict flow of fresh air to fire

Limit Fire Spread

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Fire Suppression • Sprinklers or water mist unlikely to put fire out • Attitudes are changing

– previously: sprinklers are not just ineffective, but dangerous • reduce visibility • risk of steam burns

– experience from real fires in tunnels with sprinklers/water mist generally positive

• fire grow limited → helps fire service intervention • Interaction suppression and ventilation must be considered

Limit Fire Spread

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• Importance of ventilation • Walkways • Refuges/evacuation shafts • Lighting – particularly at low level • Signage

Means of Escape Means of Escape

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Consider • Travel distances • Water supplies • Available manpower

Intervention

© Frankfurt am Main fire service Reproduced with permission

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Modern technology cannot negate the need for intelligent behaviour • Railways: staff can and should direct passengers

– Location where train stops is critical • Roads:

– Voice communication systems – Variable road signs, e.g. LED matrix

Human Behaviour Human Behaviour

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Any Questions?

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