Date of incident: September 2022
Notice of incident number: 2022178680002
Employer: Concrete product manufacturer

Incident summary
A worker was operating a fully loaded concrete mixer truck to deliver concrete mix to a workplace. The mixer truck was driving down a winding, downhill road that led to a plateau and then a final descent just above the staging area for a vehicle ferry. After completing the final descent, the mixer truck entered the oncoming lanes of traffic in which vehicles were driving off a ferry. The mixer truck turned to the right at the front of two rows of parked vehicles waiting to board the ferry and then tipped over onto its left side, resulting in serious injuries to the operator.

Investigation conclusions

Cause

• Operator unable to slow or stop vehicle due to overheated braking system. The conditions at the time of the incident, including oversized brake drums on the mixer truck (a sign of excessive wear) and a long driving time that involved a lot of braking, placed increased demands on the mixer truck’s braking systems. This resulted in the overheating of the drive axle brake shoes such that there was inadequate friction between them and the brake drums. This would have made it impossible for the operator to slow and/or stop the mixer truck when required to avoid a collision with oncoming traffic. As a result, the mixer truck made a sharp right turn — in what appeared to be an evasive manoeuvre — and then tipped over.

Contributing factors

• Overloading of equipment. The loads driven on the day of the incident were much larger than those transported previously by the mixer truck, and they imposed significant weight on the rear axles of the mixer truck. The employer did not ensure that the loads imposed on the mixer truck did not exceed the gross axle weight rating set by the Commercial Transport Regulations and the manufacturer of the mixer truck. The transport of two such loads on the same day, in combination with the braking demands imposed by the route, most likely resulted in accelerated wear and tear of the braking system components, which compromised the effectiveness of the braking system and thus the mixer truck’s ability to slow down.
• Inadequate training and supervision. The employer did not conduct an adequate assessment to confirm the operator’s ability to operate the mixer truck when exposed to real-world conditions. The employer did not demonstrate that it had provided the operator with the necessary information, instruction, training, and supervision to control all known or reasonably foreseeable health or safety hazards in his assigned work.

Other health and safety issues

• Informal health and safety program was not effective. The employer failed to implement an informal health and safety program that used regular safety meetings for the discussion of health and safety matters with its workers. Other elements of such programs, including new worker orientations, adequate inspections of equipment, and planning to ensure the mixer truck was not overloaded beyond the manufacturer’s recommendations, were also not demonstrated to have been part of the health and safety system for the workplace.

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