National Academies Press: OpenBook

Assessing and Mitigating Electrical Fires on Transit Vehicles (2021)

Chapter: Chapter 2 - Review of Data

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Suggested Citation:"Chapter 2 - Review of Data." National Academies of Sciences, Engineering, and Medicine. 2021. Assessing and Mitigating Electrical Fires on Transit Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/26288.
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Page 8
Page 9
Suggested Citation:"Chapter 2 - Review of Data." National Academies of Sciences, Engineering, and Medicine. 2021. Assessing and Mitigating Electrical Fires on Transit Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/26288.
×
Page 9
Page 10
Suggested Citation:"Chapter 2 - Review of Data." National Academies of Sciences, Engineering, and Medicine. 2021. Assessing and Mitigating Electrical Fires on Transit Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/26288.
×
Page 10
Page 11
Suggested Citation:"Chapter 2 - Review of Data." National Academies of Sciences, Engineering, and Medicine. 2021. Assessing and Mitigating Electrical Fires on Transit Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/26288.
×
Page 11

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8 Data Analysis The project team reached out to transit agencies throughout North America requesting them to provide information on fires (thermal events) they had experienced on their buses and rail cars over the last five years. Most of the systems contacted were willing to share their information, provided the system’s name was kept anonymous. The data was collected and then assembled in two separate databases, one for buses and one for rail cars. The bus database contained information on 164 thermal events that occurred at 47 different systems. Data was obtained about fires occurring on full size transit buses, commuter type buses, and small buses built on cut­away chassis. Figure 5 shows of the 164 incidents documented, 89 were electrical in nature, 35 were brake/tire related, and 21 were a result of fluid leaks. The rail database contained data on 67 thermal events that occurred at nine different systems. Three other survey recipients contacted reported no recent thermal events. Data included fires occurring on heavy rail cars, light rail vehicles, streetcars, and commuter rail cars. Figure 6 shows that of the 67 events, 12 occurred in a heater unit, 11 resulted from dragging/defecting brakes, six occurred in traction motors, and six resulted from shorted high voltage cables. Transit System Needs and Concerns In addition to the data collected in the survey, the properties surveyed filled out a short questionnaire to reflect their concerns and needs in the areas of fire prevention. The research team used this information to assist in the development of recommendations. Feedback proved difficult to obtain and resulted in fewer responses than desired. Despite sending over 50 requests for participation, the team only received responses from nine bus operators and eight rail operators. Figure 7 illustrates the responses received on a question concerning what the survey recipi­ ents consider to be the number one cause of fires in their fleet. Rail properties indicated that the high voltage cables were their main source of fires. The bus properties were split between mechanical and electrical as their main cause of fires. There was a noticeable difference in the perceived level of guidance available to mitigate fire risk between bus and rail operators. As noted in Figure 8, all but one of the rail operators rated the available guidance as either adequate or excellent. In contrast, one­third of the bus opera­ tors perceived that available information was either poor or somewhat adequate. It is important to keep in mind that with the low number of responses received, the validity of the data is in question. C H A P T E R 2 Review of Data

Review of Data 9   0 10 20 30 40 50 60 70 Electrical Exhaust Leak Friction Leak of Fluid Unknown Fire Severity, by Cause Major Minor Total Loss Figure 5. Bus fires by cause and severity. 0 2 4 6 8 10 12 14 Fires by Primary Cause Minor Major Ax le Se al Bra ke s Ca ble Sh ort ed Co llis ion Cu rre nt Co lle cto r De bri s o n R OW He ate r HV AC Sy ste m Jou rna l B ea rin g Ot he r E lec tri ca l S ho rts Mo tor Al ter na tor Pa nto gra ph Pro pu lsio n C on tro l Re sis tor Gr id Tra cti on M oto r Va nd ali sm Figure 6. Rail fires by primary cause (HVAC = heating, ventilation, and air conditioning).

10 Assessing and Mitigating Electrical Fires on Transit Vehicles Despite the partial disagreement on the availability of information, there is consensus between bus and rail operators on what additional resources are required. Figure 9 shows that both bus and rail operators agree that procurement and training are two areas where they would like to receive added support. In addition to the formal questions, the questionnaire allowed operators to share processes or strategies they have instituted to reduce fires. Some of their suggestions included: • Focusing PMI activities on preventing fire hazards; • Training technicians how to identify fire risks; • Performing proactive replacement of components to reduce failure induced fires; and • Reviewing cable and harness clamping and securing, using appropriate blocks and brackets. Figure 7. Agency reported primary source of vehicle fire (HV = high voltage; LV = low voltage). Figure 8. Perceived level of information available to mitigate fire risk.

Review of Data 11   Lastly, the survey also allowed respondents to guide future research projects and training material. Two key areas were identified by nearly half of the respondents: • Research and information needed to identify efficacy of fire suppression systems and its appli­ cation to rail cars and battery electric buses; and • Training required to help technicians identify fire risks. MaintenanceOperationsProcurement RailBus 0 1 2 3 4 5 6 7 Training Figure 9. Additional resources required.

Next: Chapter 3 - Guidance on Reducing the Incidence of Electrical Fires »
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Transit vehicle fires have safety implications for passengers and employees as well as liability implications for manufacturers, suppliers, and operators. Many of the electrical/arcing fire events experienced in the transit industry have led to a total loss of the vehicle and/or serious smoke incidents.

The TRB Transit Cooperative Research Program's TCRP Research Report 229: Assessing and Mitigating Electrical Fires on Transit Vehicles provides transit systems with information and techniques to avoid the interruption of revenue service, passenger injuries, and expenditures of operating and capital funds that occur as the result of fires on transit buses and rail vehicles.

Supplemental to the report is a Presentation describing details of the project.

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