Bus fire phobia

Being caught in a bus blaze with no escape must be one of the most harrowing experiences – and something you wouldn’t wish on your worst enemy, never mind your paying customer. Simply put, bus operators can’t afford to put their passengers at risk. FOCUS looks at efforts being made to improve fire suppression systems in buses.

Bus fires occur more frequently than you may think. In Sweden, an average of three fires in buses and coaches are reported each week, and Transport for London (TfL) experiences similar instances. The installation of an active fire protection system is an important safety measure, but these systems can be ineffective. Of concern is the lack of information regarding the performance of these suppression systems.

This prompted TfL to commission the SP Technical Research Institute of Sweden (SPTRI) to study the effectiveness of bus fire suppression systems. The latter – Sweden’s fully government-owned national institute for technical evaluation, research, testing and certification – works closely with companies, universities and institutes of technology.

Most bus and coach fires start in the vehicle’s engine compartment, usually located at the rear, making it a challenge for the driver to discover that there is a fire timeously. In the insurance industry in Sweden, the installation of fire suppression systems is actively encouraged as it is seen as a vital safety measure.

A bus has the perfect conditions for fires to start easily and spread rapidly. The compartments are compact, fuel and lubricants are among the many flammable materials present, ventilation fans produce high levels of airflow and engine parts, such as the manifold and turbocharger, can leak fuel or oil and ignite. To make matters worse, solids such as plastic and rubber are very difficult to extinguish.

Fredrik Rosen, marketing manager for the SP Department of Fire Technology explains that, when designing a fire suppression system for buses, some critical aspects need to be considered. “Presently, there is no existing international standard, and as a consequence, suppression manufacturers must verify and authenticate their systems using systems defined by relevant local or national transit authorities and insurance companies,” he says. “This can be extremely difficult, and doesn’t typically allow for comparison of different suppression systems.”

With this in mind, SPTRI decided to prepare an international fire test standard for active fire suppression systems. The work is being carried out on behalf of the National Road Authority in Sweden. The study has already reviewed all recent fire incidents in the TfL bus fleet with active installed suppression systems.

SPTRI built an engine compartment mock-up to examine the impact of various parameters. The objective of this pilot study was to construct a model of an engine compartment where different factors could be used to evaluate the fighting performance of various fire suppression systems in a well-defined and objective way.

The replicated engine compartment was typical in nature, containing all the usual bells and whistles. In the generic enclosure, different petrol-based fires were initiated and various suppression systems were used against the flames. Dry systems, water mist solutions, aerosols and gas systems were all used in the series of tests.

The results proved interesting, with the suppression systems experiencing  difficulties in certain areas. Some had challenges with the suppression of large, small or hidden fires, others had difficulty maintaining performance under high airflow, and some performed successfully even in confined spaces.

To get support from a diverse range of influential industry players, a “Reference Group” has been created. Representatives from suppression manufacturers, insurance companies, bus associations and transit authorities have joined the group and plan to present a draft proposal of the amended test standard at the spring meeting of the United Nations Economic Commission for Europe (ECE) Working Group on General Safety Provisions (GRSG) in Geneva.

Plenty of leading industry professionals are on board to provide constructive insight and contributions – including bus manufacturers Volvo, Scania, Daimler, MAN, Gillig and Motor Coach Industries, together with the transit authorities of London, Chicago, Los Angeles Transit, São Paulo and Western Australia.

It is hoped that the GRSG will vote for and accept proposed amendments to ECE regulation 107* as this would make the installation of fire suppression systems in engine compartments mandatory for all single-deck, double-deck, rigid or articulated vehicles of category M2 or M3.

“Currently, ‘performance requirements‘ are prescribed by local transit authorities in their contracts with transport providers,” says Rosen.

“Clearly, a standardised approach with broad acceptance would simplify the inherent problems. Ideally, this would be in the form of an ECE regulation, or, alternatively, an international standard with broad market acceptance that could provide the basis for a level playing field for manufacturers.”

In the interim, SPTRI has started working on rules for its own voluntary certification system, known as the P-mark, as can be seen on various products boasting quality assurance certification. A P-mark certificate means a product meets the requirements of relevant standards and regulations, making sure the manufacturer or importer has operated within an approved inspection and quality control scheme.

SPTRI has taken a new approach to fire suppression systems and aims to create a safer environment for both passengers and drivers. By installing improved fire suppression systems in engine compartments, it will allow for a safe exit, particularly for the most vulnerable passengers – the elderly, disabled and children. The prospect of an amended international standard where critical safety aspects are considered is encouraging, and something to keep an eye on.

* Concerning the adoption of uniform technical prescriptions for wheeled vehicles, equipment and parts, which can be fitted and/or be used on wheeled vehicles and the conditions for reciprocal recognition of approvals granted on the basis of various prescriptions; previously amended in 1995.