bus safety investigation report

BUS

Safety Investigation Report

Engine Bay Fire Tongarra, NSW 3 September 2018

BUS SAFETY INVESTIGATION REPORT

Engine Bay Fire Tongarra, NSW 3 September 2018

Released under the provisions of Section 45C (2) of the Transport Administration Act 1988 and Section 46BBA (1) of the Passenger Transport Act 1990 OTSI File 04804 Cover photo source: Premier Motor Service

Published by: The Office of Transport Safety Investigations

Postal address: PO Box A2616, Sydney South, NSW 1235

Office location: Level 17, 201 Elizabeth Street, Sydney NSW 2000

Telephone: 02 9322 9200

Accident and incident notification: 1800 677 766

Email: [email protected]

Website: www.otsi.nsw.gov.au

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Investigations has been obtained.

THE OFFICE OF TRANSPORT SAFETY INVESTIGATIONS

OTSI is an independent NSW authority which contributes to the safe operation of bus,

ferry and rail passenger and rail freight services in NSW by investigating safety

incidents and accidents and transport safety risks, identifying system-wide safety

issues and sharing lessons with transport operators, regulators and other

stakeholders.

OTSI is empowered under the Transport Administration Act 1988 to investigate rail,

bus, and ferry accidents and incidents in accordance with the provisions of the

Passenger Transport Act 1990 and Marine Safety Act 1998. It also conducts rail

investigations on behalf of the Australian Transport Safety Bureau under the Transport

Safety Investigation Act 2003 (Cth).

OTSI investigations are independent of regulatory, operator or other external entities.

OTSI investigates using a ‘no-blame’ approach to understand why an occurrence took

place and to identify safety factors that are associated with an accident and incident,

to make recommendations or highlight actions that transport operators, regulators and

government can take to prevent recurrence and improve safety.

Evidence obtained through an OTSI investigation cannot be used in any subsequent

criminal or disciplinary action. However, a regulator can undertake its own

investigation into an incident OTSI has investigated and coronial inquiries can obtain

access to OTSI information.

OTSI does not investigate all transport safety incidents and accidents but focuses its

resources on those investigations considered most likely to enhance bus, ferry or rail

safety. Many accidents result from individual human or technical errors which do not

involve safety systems so investigating these in detail may not be justified. In such

cases, OTSI will not generally attend the scene, conduct an in-depth investigation or

produce an extensive report.

OTSI may request additional information from operators or review their investigation

reports which may lead to a number of actions, such as the release of a Safety

Advisory or Alert to raise industry awareness of safety issues and action.

OTSI investigators normally seek to obtain information cooperatively when conducting

an investigation. However, where it is necessary to do so, OTSI investigators may

exercise statutory powers to conduct interviews, enter premises and examine and

retain physical and documentary evidence.

Publication of the investigation report

OTSI produces a written report on every investigation for the Minister for Transport

and Roads, as required under section 46BBA of the Passenger Transport Act 1990.

Investigation reports strive to reflect OTSI’s balanced approach to the investigation,

explaining what happened and why in a fair and unbiased manner. All DIPs will be

given the opportunity to comment on the draft investigation report.

The final investigation report will be provided to the Minister for tabling in both Houses

of the NSW Parliament in accordance with section 46D of the Passenger Transport

Act 1990. The Minister is required to table the report within seven days of receiving it.

Following tabling, the report is published on the OTSI website – www.otsi.nsw.gov.au

– and information on the safety lessons promoted to relevant stakeholders.

http://www.otsi.nsw.gov.au/

OTSI Bus Safety Investigation

Bus fire, Tongarra, 3 September 2018 i

CONTENTS

TABLE OF FIGURES ii

EXECUTIVE SUMMARY iii

PART 1 FACTUAL INFORMATION 1

The occurrence 1

Location 2

Environmental information 2

Operator information 3

Bus information 3

Related occurrences 3

PART 2 ANALYSIS 4

Introduction 4

Damage 4

Initiation and spread of fire 6

Evacuation of bus 12

Fire extinguisher and alarms 12

PART 3 FINDINGS 13

Contributory factors 13

Other findings 13

PART 4 RECOMMENDATIONS 14

Bus operators 14

PART 5 APPENDICES 15

Appendix 1: Sources and References 15


Bus fire, Tongarra, 3 September 2018 ii

TABLE OF FIGURES

Figure 1: Location map 1

Figure 2: Engine bay of 7257 MO 5

Figure 3: Engine bay of same model bus, 7294 MO 5

Figure 4: Fuel line misalignment 1 7

Figure 5: Fuel line misalignment 2 8

Figure 6: Fuel line fittings 8

Figure 7: OEM body build instruction (BBI) 9

Figure 8: Typical barb type fuel banjo fitting, bolt and sealing washers 9

Figure 9: Diesel fuel residue from ruptured fuel line 10

Figure 10: Rotational heat patterns 10

Figure 11: Location of electrical short circuit 11

Figure 12: Testing continuity of A/C system main fuse and battery main switch 11


Bus fire, Tongarra, 3 September 2018 iii

EXECUTIVE SUMMARY

On Monday 3 September 2018, the driver of a Premier Motor Service bus was

travelling on the Illawarra Highway near Tongarra when they noticed the engine bay

fire suppression system alarm had activated. The driver stopped the bus and

inspected the cause of the alarm and found smoke emitting from the engine bay area.

The driver evacuated the sole passenger from the bus then attempted to extinguish

the fire, however the fire continued to burn. Fire and Rescue NSW attended the scene

and extinguished the fire, however the bus was severely damaged by the fire and was

later determined a total loss.

There were no reported injuries to any person.

The investigation found that the fire was likely initiated from a fuel leak from a damaged

fuel line. Once the fire had begun, it was perpetuated by a continual supply of diesel

fuel and other combustible material in the engine bay.

The investigation also found that the power from the batteries to the engine bay was

still live, despite the driver turning the ignition off. This meant the fire could reignite

following the discharge of the fire suppression system.

OTSI recommended that the bus operator review maintenance and inspection

systems to ensure the integrity of fuel system components.

Full details of the Findings and Recommendations of this bus safety investigation are

contained in Parts 3 and 4 respectively.


Bus engine bay fire, Tongarra, 3 September 2018 1

PART 1 FACTUAL INFORMATION

The occurrence

1.1 At approximately 15101 on Monday 3 September 2018, while travelling along

the Illawarra Highway at Tongarra, south of Wollongong (Figure 1), the driver

of a Premier Motor Service (Premier) bus 7257 MO was alerted to a possible

fire by the engine bay fire suppression system (EBFSS) alarm. The alarm also

indicated that the EBFSS had discharged.

Source: Google, annotated by OTSI

Figure 1: Location map

1.2 The driver then located a safe area and brought the bus to a stop and secured

the vehicle. The driver alighted from the bus to investigate the cause of the

alarm and discovered smoke emitting from the engine bay area. The driver

then returned to the front door and instructed the sole passenger on board to

evacuate.

1 Times in this report are in 24-hour clock format in Australian Eastern Standard Time (AEST): Coordinated Universal Time (UTC) + 10 hours



1.3 Review of the vehicle’s CCTV showed a member of the public offered

assistance and called emergency services while the driver retrieved the fire

extinguisher from the bus.

1.4 The driver attempted to extinguish the fire, however the fire continued to burn.

The driver then contacted the Premier control room and notified it of the

situation.

1.5 The CCTV footage showed the intensity of the fire increasing, up until the

recording ceased at approximately 1514.

1.6 Fire and Rescue NSW attended the scene and extinguished the fire, however

the bus was severely damaged by the fire and was later determined a total

loss.

1.7 A Fire and Rescue NSW Hazmat team were also deployed to decontaminate

the road surface for diesel fuel residue adjacent to and leading up to the

incident location.

Location

1.8 The incident occurred in the rural locality of Tongarra, located in the

Shellharbour Local Government Area (LGA) approximately 113 km southwest

of Sydney’s CBD. At the time of the incident, the bus was travelling westbound

on the Illawarra Highway, eventually stopping 250 m from the intersection with

Tongarra Mine Road.

Environmental information

1.9 At 1500, the Bureau of Meteorology recorded a temperature of 12.2˚ C with a

south by south-westerly wind of 11 km/h at Albion Park weather station, which

is approximately 13 km from the incident site.

1.10 Apart from the likely effect of wind on the promotion of the fire and the

dispersal of smoke, it was determined that the environmental conditions

played no part in the incident.



Operator information

1.11 Premier’s operations and maintenance are based in the Wollongong suburb

of Unanderra. The company provides services under Transport for NSW’s

Outer Sydney Metropolitan Bus Service Contracts Region 9 (OSMBSC009)

as well as various services including charter, tourist and educational transport

services. Premier has a mixed fleet of approximately 196 buses and coaches.

Vehicle 7257 MO was operated and maintained from a satellite depot at

Shellharbour.

Bus information

1.12 The bus was a diesel fuelled 2013 model Iveco Metro Delta Euro 5. The body

was manufactured by Volgren Australia Pty Ltd and was registered in NSW

as 7257 MO. Maintenance records showed that the bus had travelled less

than 150,000 km and had a routine 12 monthly service on 29 August 2018.

There were no defects detected relevant to this incident.

1.13 A Heavy Vehicle Inspection Scheme (HVIS) inspection was conducted by the

Roads and Maritime Services2 (RMS) on 17 August 2018. No defects were

recorded as a result of this inspection.

1.14 The bus was authorised to carry 58 seated passengers. At the time of the

incident there was one passenger on board.

1.15 There were no previous reported fire incidents for this bus.

Related occurrences

1.16 During the course of this investigation, OTSI investigators deployed to another

fire involving a coach with a similar model engine and fuel arrangement as

fitted to 7257 MO. The incident occurred in January 2019 at Shoal Bay, NSW.

In this instance, it was found that a fuel leak had propagated from a fuel fitting

fitted to the secondary fuel filter as that observed on 7257 MO. The

2 On 21 November 2019, NSW Parliament passed legislation that enabled the full integration of Transport for New South Wales (TfNSW) and RMS into one organisation. Effective as at 1 December 2019, RMS was dissolved and its functions became the functions of TfNSW.



circumstances of the initiation, propagation and damage caused by the fire

were near identical to that observed in this investigation.

PART 2 ANALYSIS

Introduction

2.1 OTSI analysed several sources of information relating to the incident in parallel

with an inspection of the bus following the event.

2.2 These sources included an internal investigation report and service history of

the bus submitted by Premier, HVIS inspection records, the National Heavy

Vehicle Inspection Standards (NHVIS), CCTV footage from the bus and the

driver’s version of events.

2.3 The investigation focused primarily on the factors that contributed to the

initiation of the fire, evacuation of passengers, maintenance of the vehicle and

driver training.

Damage

2.4 The majority of the fire damage was confined to components within the rear of

the engine bay, aluminium bulkhead and corner panels, rear engine bay access

panels and fibreglass exterior rear panels (see Figures 2 and 3).

2.5 The passenger saloon area was severely heat affected with some plastic and

foam components consumed by fire.

2.6 Heat damage was also evident throughout the engine bay area and battery

compartment.

2.7 The engine cooling system heat exchanger (radiator) assembly was mostly

unaffected by the fire.



Source: OTSI

Figure 2: Engine bay of 7257 MO

Source: OTSI

Figure 3: Engine bay of same model bus, 7294 MO



Initiation and spread of fire

2.8 Examination of the diesel fuel system indicated that a fuel leak likely initiated at

a pinch point within the fuel supply line (see Figures 4, 5, 6, 7 and 8). Due to its

proximity to the engine cooling fan assembly, it is likely that fuel leaking from

this fitting was spread throughout the engine bay by the air flow from the cooling

system fan. When the vehicle was inspected following the fire, diesel fuel

residue was evident on the pressurised fuel filter assembly and cooling fan

support frame (see Figure 9).

2.9 It is likely that fuel from this point came into contact with hot engine exhaust

components, causing the fuel to vaporise. Once vaporised, the fuel likely

contacted an ignition source such as an electrical spark generated by the

alternator slip ring brushes.

2.10 As the fuel filter is located on the pressure side of the fuel system, fuel would

continue to flow unimpeded without adversely affecting the performance of the

vehicle. Statements made by the driver of the bus and CCTV recordings

confirmed that the vehicle operated without issue up to and including the point

where the driver shut it down following activation of the EBFSS.

2.11 Fire damage was observed on several drive pulleys and the cooling fan

assembly, which likely indicated that the fire was active while the engine was in

operation (see Figure 10). Similarly, the lack of heat damage to the aluminium

cooling system heat exchanger core, likely indicates that the cooling fan was

rotating during the commencement of the fire event, drawing cooling air into the

engine compartment.

2.12 Inspection of the vehicle revealed that within the area adjacent to the engine

cooling fan assembly and panels directly adjacent to this area appeared to be

more heat affected than the rest of the engine bay area.

2.13 The main battery positive and air-conditioning (A/C) cables exhibited evidence

of electrical short circuiting3. When tested for continuity4, the main A/C feed

3 ‘A short circuit is when there is direct contact between a current carrying conductor and another conductor.’ - Kirk’s fire investigation (2012) DeHaan. J.D.; Icove.D.J. 7th Ed. p.79. 4 Continuity testing is the act of testing the resistance between two points in an electrical circuit or component. If there is very low resistance (less than a few ohms), the two points are connected electrically and is commonly known as a closed circuit.



circuit fuse indicated near to zero resistance which indicates electrical current

was still being supplied to the short circuit area via the main fuse (see Figure

12).

2.14 The main battery isolation switch was unable to be operated at the time of the

fire due to its proximity to the fire activity within the engine bay area (see Figure

12).

2.15 It is likely that the continuing flow of energy from the main A/C feed to the site

of the short circuit and the presence of residual diesel fuel, reignited the fire

following discharge of the EBFSS (see Figure 11).

Source: OTSI

Figure 4: Fuel line misalignment 1



Source: OTSI

Figure 5: Fuel line misalignment 2

Source: OTSI

Figure 6: Fuel line fittings



Source: IVECO Australia – annotated by OTSI

Figure 7: OEM body build instruction (BBI)

Source: OTSI

Figure 8: Typical barb type fuel banjo fitting, bolt and sealing washers



Source: OTSI

Figure 9: Diesel fuel residue from ruptured fuel line

Source: OTSI

Figure 10: Rotational heat patterns



Source: OTSI

Figure 11: Location of electrical short circuit

Source: OTSI

Figure 12: Testing continuity of A/C system main fuse and battery main switch



Evacuation of bus

2.16 At the time of the incident, the driver was nearing the end of the service and

only one passenger was on board. A review of the on-board CCTV recording

showed that when the driver was alerted by the EBFSS alarm and he had

brought the bus to rest, he notified the passenger to evacuate the bus.

2.17 The door controls functioned as required and the driver and passenger alighted

from the bus without injury or accident.

Fire extinguisher and alarms

2.18 An Australian Design Rule (ADR 58/00)5 specified that buses were to be

equipped with a readily accessible fire extinguisher selected and located in

accordance with the applicable Australian Standard6. Located next to the

driver’s seat was a 2.5 kg Dry Chemical Powder fire extinguisher7.

2.19 The EBFSS had a fire/heat warning sensor system that consisted of a

pressurised detection line placed in the engine compartment. When any part of

the detection line is heat affected and bursts, the system discharges a water

based fire suppressant agent including an aqueous film forming foam (AFFF).

The AFFF component is designed to cover any residual combustible liquid

fuels. The EBFSS also provides audible and visual dashboard alarms.

5 Australian Design Rule 58 Requirements for Omnibuses Designed for Hire and Reward 2006 6 Portable fire extinguishers and fire blankets – Selection and location. Australian Standard (AS) 2444—2001. 7 Routine service of fire protection systems and equipment. Australian Standard (AS) 1851—2012. AS 1851 required this type of extinguisher to be checked every six months. The EBFSS attached service record indicated it was last checked in March 2018.



PART 3 FINDINGS

From the evidence available, the following findings are made with respect to the fire

on bus 7257 MO at Tongarra, NSW.

Contributory factors

3.1 The fire was likely initiated from a diesel fuel leak perpetuated by a short circuit

of the air conditioning wiring. Once the fire had begun it was fueled by diesel

fuel and other combustible material in the engine bay.

3.2 The fuse for the A/C remained intact, supplying a continuous source of energy

to the short circuit of the main A/C cable.

3.3 The power from the batteries to the engine bay was still live despite the driver

turning the ignition off. This meant the fire could reignite after discharge of the

EBFSS.

Other findings

3.4 The driver was unable to extinguish the fire using the on-board fire extinguisher.

3.5 The engine bay fire suppression system activated, but it is likely that, while

initially suppressing the fire, the fire reignited due to a continual supply of

energy to the short circuit of the A/C main cable.



PART 4 RECOMMENDATIONS

It is recommended that the following additional safety actions be undertaken by the

specified responsible entities.

Bus operators

4.1 Review maintenance and inspection systems to ensure the integrity of fuel

system components.



PART 5 APPENDICES

Appendix 1: Sources and References

Sources of information

• Premier Motor Service

• Transport for NSW

References

• Australian Design Rule 58 – Requirements for Omnibuses Designed for Hire and

Reward 2006

• Australian Standard (AS) 2444—2001. Portable fire extinguishers and fire blankets

– Selection and location.

• Australian Standard (AS) 1851—2012. Routine service of fire protection systems

and equipment

• DeHaan. J.D.; Icove.D.J., Kirk’s Fire Investigation (2012) Pearson 7th Ed.

bus safety investigation report

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