Fires in mass transportation, and buses specifically, have been a long-term concern. The very nature of these systems puts a large number of people in a small space for efficiency. However, most still have only two primary points of egress (of course, all modern transit does allow for emergency exits as well, but these are rarely utilized except where the primary exits become inaccessible).
Compounding the limited egress options are an ageing population that increases the evacuation time and hotter-running engines with regeneration in the exhaust systems to enable lower emissions but leading to a potentially greater fire risk.
According to the National Fire Protection Agency (NFPA), there are an average of 4.24 bus fires in the US each day. As with any risk there are always efforts to mitigate the risk. The focus for fire suppression on buses has long been the engine area. Studies by the NFPA show that nearly 70% of bus fires are attributed to the engine, running gear or tyres and that 83% are a result of mechanical or electrical failures. These percentages are also supported by a Swedish study which found 61% of fires originate in the engine area.
In buses, automatic fire suppression systems have been increasing in use since the mid-1980s. While there have been many standards and evaluations for bus fire systems, most local, that have existed for years, in the early 2000s an initiative began to create a regulation for European buses to be protected against fire as well as a standardized means of evaluation.
Around that time, RISE (formerly known as the SP Institute), in conjunction with industry stakeholders, developed a test method SP 4912 and certification known as P Mark SPCR 183. These tests were targeted specifically on evaluating fire-suppression system effectiveness in the engine area on buses. Ultimately SP 4912 became the basis for the European standard UNECE Regulation R107 for fire systems, which was phased in by bus type starting in 2019 and is now in place for new buses destined for the European market, no matter the location of manufacture.
The test scenarios include high fire load, low fire load and hidden fires, each at varying airflows of 0.0, 1.5 and 3.0m/s, along with tests for class A fires and a unique test to ensure a system guards against fire reignition. Each test provides for the placement of the test fires, pre-burn requirements, airflow timing and limitations on nozzle placement. The tests are conducted by an independent third party and provide for an excellent comparison basis for the effectiveness of different agents. However, with certifications only providing a ‘pass’ or ‘fail’ much of this valuable data remains overlooked.
Recent changes to the testing methods
As with almost anything, there were opportunities for improvement and RISE added a rating system to its SP 4912 test standard. While the testing required a score of a minimum of 6 out of 10 tests to be passed for SPCR 183 certification and only 4 of 11 for R107 certification, initially the standards only provided for a system to be approved or not approved – without indication of the underlying score. As such, a system that minimally passed received the same approval as one that had been effective across the tests.
In 2019 SPCR improved the rating system with the release of a ‘Test Scenario Rating’ based on the various test scenarios passed, with ratings from a low of ‘E’ all the way up to an ‘A+’ award for passing all the tests. Newer SPCR 183 certificates now include the criteria for the scenario rating, but for early certificates lacking the rating it is easy to determine based on the tests passed with the details provided in SP 4912.
For those creating bus specifications, these ratings have created an easy yet valuable additional evaluation criteria to add to bus fire-system requirements. By the very nature of fires on buses, it is impossible to guess what type of fire will start in any particular bus, so ensuring the fire system has passed all testing will go a long way to ensuring a positive outcome. Average can be OK sometimes, but when life safety is on the line, ensuring the best systems are selected can have a dramatic effect.
With each of the test scenarios designed to replicate known engine fire types, failure to pass any scenario opens the possibility that the fire will not be efficiently dealt with, putting lives in danger. While budgets are always a concern, in looking at the pricing of qualified systems, there is not a direct relationship between increased performance and the cost of the system. Further, the cost of the system is only one component of cost; installation and maintenance costs must also be factored into the overall lifetime costs of the systems.
Standards adoption beyond Europe
While the UNECE R107 is obviously targeting Europe, its effect has been felt far beyond the region. Countries around the world from south-east Asia to the Middle East and in central and south America – especially those who are very dependent on bus transport – have adopted the standard for themselves to ensure that their ridership is safe and protected by a system that has had a proper evaluation. Many are now also incorporating the ‘Test Scenario Rating’ as part of their specification to ensure a system provides the highest levels of safety.
In the US, while no national requirement has been developed, many major cities have added either the SPCR 183 or UNECE R107 as part of their system specifications. Further, following the US National Transportation Safety Board’s recommendation that all school buses be equipped with automatic fire-suppression systems has left school districts and bus manufacturers alike the task of finding and evaluating fire-system options. Many are also looking to the European standards.
With Europe leading the way in fire-safety requirements for buses, so many others are taking notice not only of the fire awareness but also how to select a system to provide proper protection. With so many models of buses, both new and existing, it would be impossible to run full-scale fire tests on every bus. However, by looking to the European standards R107 and the even more stringent SPCR 183 (both using the testing method SP 4912 as a basis for their certification) and by selecting a system with the highest score, owners and operators of buses and coaches will go a long way to provide the safety level they are seeking for the fleet and customers.
For more information, go to www.reactonfire.com