Bus Safety Investigation - Bus fire MO5103 - Campbelltown - 16 August 2021

View the Bus Safety Investigation Report

What happened

On the morning of 16 August 2021, bus MO5103 operated by Busabout caught fire on Kellicar Road, Campbelltown, in the vicinity of Macarthur Square Shopping Centre. Immediately before, the bus was travelling southbound with the driver and three passengers. One of the passengers observed smoke in the back of the bus and the driver was alerted.

The driver stopped the bus in a safe location and all onboard safely evacuated. Smoke escalated to fire, which spread and engulfed the bus. Fire and Rescue NSW attended and extinguished the fire. The bus was destroyed.

What we found

The investigation identified that the initiating source of the fire was within the roof-mounted air conditioning (A/C) system. The A/C system was manufactured by DENSO Automotive Systems Australia, controlled by a Thoreb M2 programmable node.

The investigation found damage associated with electrical arcing in the vicinity of the control node, specifically in the region of the main connector block and its associated wiring harness. While the specific failure/s leading to the fire could not be determined, several potential contributing factors were examined.

Actions taken by directly involved parties during the investigation



DENSO

• Initiated comprehensive engineering inspections of the A/C systems of similarly configured buses immediately after the incident. 
• Made recommendations to Busabout  for rectifying wiring issues identified as part of this process.

Busabout

• Initiated comprehensive engineering inspections of the A/C systems of similarly configured buses immediately after the incident. 
• Rectified all identified wiring issues.

Transport for NSW

• Reviewed the current bus battery isolation requirement, and compliance with the T BU FL 01701 ST Mounting and Installation of Electrical Equipment Standard, Version 1.0, Issue date: 3 April 2019. 
• Reviewed alternative safe work practices of power isolation to the vehicle in the event of a thermal/fire occurrence. 
• Reviewed all relevant emergency procedures and current training programs undertaken for bus fires and thermal events. 
• Risk assessed the flammability and combustibility of materials used to manufacture bus bodies. Recorded and documented the identified controls to consider options to incorporate into the current Divisions’ risk mitigation strategies.  

Recommendations

OTSI made the following recommendations:

Bus and coach operators

• Review maintenance regimes to ensure inspections adequately address and remedy any issues with wiring integrity, security and overall cleanliness of the air conditioning system.
• Ensure manufacturer specifications for contact resistance limitations of the Tyco S2 connector, for a maximum of 25 removal/replacement cycles, are incorporated into asset management and maintenance regimes (for operators of buses configured with a DENSO air conditioning system, controlled by a programable Thoreb M2 node).

Transport for NSW 

• Consider reviewing the framework for asset systems configurations to ensure that critical design decisions related to high current systems are documented and available to operators and maintainers.
• Consider reviewing current asset management requirements to apply a more comprehensive safety risk management and regulatory framework, for long-term asset management.