Safety Alert

What Happened

A loaded CAT 793 haul truck experienced an uncontrolled rollback of approximately 8 metres on the Pit 4 haul ramp (12% grade) when the operator selected the wrong gear after stopping for a radio communication. The truck rolled backward before the operator applied the service and park brakes, coming to rest approximately 15 metres from a water cart that was ascending the ramp behind it.

Why It Matters

A loaded CAT 793 weighs approximately 370 tonnes. An uncontrolled rollback on a grade can quickly become unrecoverable, especially if the braking system is overwhelmed. The water cart and its operator were directly in the path of the rolling truck. Had the truck not been stopped, a collision at this weight differential would almost certainly be fatal.

Immediate Actions Required

1. 1All haul truck operators to receive refresher training on gear selection procedures on grades — emphasis on maintaining brake application during gear changes
2. 2Minimum following distances on haul ramps to be reviewed and increased — signage to be updated
3. 3Implement a mandatory radio-free zone on haul ramps with grades exceeding 10%
4. 4Haul truck retarder and brake systems to be inspected and function-tested on all units
5. 5Review and update the traffic management plan for Pit 4 haul ramp

Key Learning

When stopped on a grade in a loaded haul truck, the park brake must be applied before any gear changes. Never take your foot off the brake to change gears on a grade without the park brake engaged. Distraction — including radio communications — on a grade is a recipe for disaster. Manage one task at a time.

Discussion Points for Toolbox Talk

• •What is your procedure for stopping and restarting on a grade in a loaded truck?
• •Have you ever experienced a rollback event? What caused it and what did you do?
• •Should we implement a no-radio policy on steep haul ramps? What are the pros and cons?