Fires in buses, trucks, construction equipment and other heavy vehicles are common around the world and annually involve substantial public cost. For instance, fires in mines are predominantly caused by service vehicles, drilling rigs and loaders [1, 2], and statistical data indicates that 0.5-1 percent of the buses registered in northern Europe will suffer an incident related to fire each year [3, 4, 5].
The consequences of a vehicle fire depend on the fire scenario, vehicle type and fuel, surrounding environment, and means for fire mitigation. Underground mines, tunnels and cities are environments where a vehicle fire may have dramatic consequences, especially in combination with fuels such as compressed natural gas or compressed hydrogen used in fuel cell vehicles. For buses, the time for evacuation is crucial, and early fire detection and means for fire suppression can be vital [6, 7].
In case of a fire in a vehicle, passive and active fire safety systems and means for safe evacuation are very important. This include fire detection and suppression systems, portable fire extinguishers, fire resistant partitions, shut-off devices for fuel and electricity, fire resistant insulation and fabrics, evacuation routes and emergency exits, etc. All this is part of vehicle fire risk management. However, fire risk management shall also include e.g. regular risk assessments, training and improved quality procedures to address the problem already before the fires arise. An improvement of the fire risk management procedures for vehicle manufacturers, operators and service centres have potential to greatly reduce the number of fires and to enhance the fire protection for those incidents that still occur.
RISE has initiated and is currently working on a certification scheme for the vehicle industry. The certification will enable manufacturers, operators and service centres (workshops) to certify their fire risk mitigation process, including requirements on fire risk assessments. The company must be able to assure the quality of their design/production/operation/maintenance process in order to secure a high level of safety and to keep the risks as low as reasonably practical. The fire risk management required in the certification is a key safety element, used to identify and evaluate fire hazards. In the process, identified hazard must be documented together with suitable remedies aiming at control or elimination of the hazard. If no action is recommended for a specific hazard, the documentation should clarify this decision.
Certification is composed of the following five elements:
Fire safety training
Education and training of design engineers, quality control inspectors, managers, drivers and maintenance personnel is the basis of the certification. This includes training in vehicle fire risk management as well as study of fire hazards and mitigation methods specific to different types of vehicles and fuels.
Fire risk management
The client must do regular fire risk assessments, i.e. a systematic study to identify fire hazards, and document decisions for risk elimination, control or acceptance. The input from the fire risk assessment should be used for future design improvements, enhancements to maintenance documents, enhancement to operation manuals and practices, replacement cycles of critical components etc.
Reporting of thermal events – database
The client must have procedures for linking information, data and experience from actual thermal events in the field to relevant personnel, including design engineers, quality control inspectors, drivers and maintenance personnel. A database of actual thermal events can be used for research purposes, increasing fire safety of vehicles worldwide.
Quality procedures and configuration management
The client must have documented procedures for quality control. There shall be quality procedures in place to manage and mitigate the risks that arise or are found, and procedures ensuring that findings are linked to design engineers, fleet managers, drivers, maintenance personnel, etc., such that they are resolved properly. All previous described elements of the certification shall be incorporated in the company’s quality control system.
Annual inspections shall ensure that the client fulfils the requirements in the certification rules.
The certification system is based on experience and knowledge gained through research, fire investigations and other industry professional services. The content is in line with the recommendations of a new research report “Motorcoach and School Bus Fire Safety Analysis” , ordered by Federal Motor Carrier Safety Administration (FMCSA) in the US. The recommendations include enhanced data quality and reporting, operational training, vehicle design and safety equipment, and inspection standards.
At present, RISE has developed certification rules for vehicle manufacturers as well as a specific method for vehicle fire risk management [9, 10]. The method particularly provides elaborate support for identification of fire hazards in newly assembled vehicles as well as fire hazards resulting from operation, maintenance and retrofitting of the vehicles. One can use the method, which provides examples as well as checklists, as a tool in the hazard identification process. Visual inspection is the basis for identification of fire hazards and includes inspection of the electrical systems, the hydraulic, lubrication, pneumatic and fuel systems, the exhaust system, brakes and tyres, and others. To enhance the visual inspection there are also guidelines for the use of thermal imaging camera, which can identify potential fire hazards, primarily in the electrical system, concealed from a traditional visual inspection. Other useful tools are multimeter, endoscope and temperature strips.
The method also presents how the identified hazards can be translated to estimations of fire risks and how these can be evaluated. There are several different estimation methods that could be used, and most of them are based on estimations of the likelihood and consequence of the identified hazardous events. The evaluation aims to provide an overview of the risk image and to separate the risks which need to be addressed from risks that are acceptable. Figure above gives an example of a risk assessment matrix that can be used for this purpose.
The risk assessment (identification, estimation and evaluation) should be followed by risk reduction. Risk reduction measures can be considered in following four areas:
- Risk elimination or minimization by design
- Passive and active fire protection systems
- Improved maintenance and cleaning procedures
- Improved training and quality procedures
The published method gives recommendations on fire risk reduction measures for common designs, procedures and systems. A few examples that can be crucial are:
- Keep conductors without preceding fuses as short as possible and position main fuses already in the battery box. Provide a main switch adjacent to the batteries to isolate power to the vehicle if required, including starter/generator circuit.
- Be aware that rubber may be conductive and do not use any unspecified rubber for isolation purpose of the electrical system.
- Avoid construction solutions where failed fuel lines could spray fluid onto exhaust pipes, turbo charger or other hot parts of the exhaust system.
- Monitor tyre pressures, which is especially important for dual-wheels.
- Monitor critical temperatures of brake systems and use fire resistant material for wheel housings.
- Use an automatic or semi-automatic fire suppression system in the engine compartment.
- Clean engine area and transmission area regularly, allowing no build-up of flammable deposits and facilitating detection of possible leakages.
- Training for drivers
- Always react on any warning light and regularly monitor air pressure gauges, temperature gauges for overheating, coolant temperature gauge and engine oil pressure gauge. Note that ABS warning light may indicate a wheel bearing failure.
- Never ignore electrical misbehaviour.
- Ensure knowledge of correct emergency response procedures.
The new method for fire risk management in vehicles is a hands-on and important guideline, which together with enhanced quality procedures and training of the personnel form the basis for the certification aiming to reduce the number, and to limit the consequences, of vehicle fires.
For best results, it is important that manufacturers, operators and service centres are equally dedicated to solve the fire problem. Vehicle fire investigations reveal that design, production, operation and maintenance can all be responsible, however, most important is to ensure that information and experiences from fire incidents and identified fire hazards are linked to relevant personnel, practices, manuals, and quality procedures.
The new certification scheme will allow personnel, strategies, and techniques involved in fire safety mitigation of new and existing vehicles, to be kept at the highest performance level. The certification cannot be a guarantee for elimination of vehicle fires but ensuring that manufacturers, operators and service centres will operate at the front line of vehicle fire safety engineering.
- R. Hansen, “Design fires in underground hard rock mines,” Licentiate Thesis 127, School of Sustainable Development of Society and Technology, Mälardalen University, Västerås, Sweden, 2011.
- H. Sönksen, “Oral presentation at the Symposium on Fire Protection for Vehicles and Work Equipment Underground,” Freiberg, Germany, 2009.
- A. Rakovic, M. Försth and J. Brandt, “Bus Fires in Sweden,” SP Technical Research Institute of Sweden, SP Report 2015:43, 2015.
- A. Hofmann and S. Dülsen, “Fire safety performance of buses,” Proceedings of FIVE – Fires In Vehicles, Chicago, USA, 2012.
- E. Kokki, “Bus Fires in 2010-2011 in Finland,” Proceedings of FIVE – Fires in Vehicles, Chicago, USA, 2012.
- Swedish Accident Investigation Authority, “Slutrapport RO 2013:01, Brand med två biogasbussar i stadstrafik i Helsingborg, Skåne län, den 14 februari 2012,” ISSN 1400-5743, 2013.
- Office of Transport Safety Investigations (OTSI), “Technical inspection findings, Fire involving Transdev Shorelink Bus MO1970, Mount Colah, 16 December 2011,” Sydney, Australia, 2011.
- John A. Volpe National Transportation Systems Center (Volpe), “Motorcoach and School Bus Fire Safety Analysis,” U.S. Department of Transportation (USDOT), Federal Motor Carrier Safety Administration (FMCSA), USA, 2016.
- SPCR 190, “Certification rules for vehicle manufacturers with respect to vehicle fire safety,” SP Certification, Borås, 2016.
- SP Method 5289, “Fire risk management procedure for vehicles,” SP Technical Research Institute of Sweden, Borås, 2016.