After loading concrete blocks onto a drawbar vehicle (known also as wagon and drag), the contractor driver exited site and seconds after, the rear trailer became uncoupled and narrowly missed a third party person who was working on an adjacent construction site.

Fortunately, the worker who was in the ‘line of fire’ only suffered a few grazes – but this had the potential to be far more serious!

Please watch the figure in the top left of image circa 16 seconds into this dramatic video   Please also share the learning points with your colleagues.

CEMEX has provided a HiPo alert that can be easily shared or this Safequarry Alert, which is based on the CEMEX alert, could be used.

The images below show the site before and after the incident occurred. Anyone in the path of the trailer when the incident occurred could have easily been killed

Sequence of events

• The driver had been operating the vehicle the previous day, but as a rigid only and therefore had dropped the drawbar trailer in the haulier’s depot.
• On the day of the incident, the driver re-connected the drawbar and completed a tug test to ensure the connection was secure before completing his vehicle walkaround checks.
• He then drove for just over 30 minutes from his depot to the block plant for loading.
• The vehicle was loaded, the driver strapped and checked the load before leaving.
• Just after this, the driver said that it felt like he had caught the heras fencing at the adjacent construction site, but this was actually the motion of the trailer becoming detached.
• He stopped immediately and realised what had happened, checked everyone was alright before reporting this to his office and the site.
• The vehicle was recovered and a full inspection by 2 different external specialists was carried out who both confirmed there were no defects with the vehicle or the coupling system.
• The driver commented that he must not have connected the drawbar correctly.

• The likely cause was the red safety interlock not being engaged correctly, causing the pin to work its way loose.
• A similar issue was previously identified by a competitor, who found that operating the vehicle with the coupling in the open position allowed dirt and debris to prevent the interlock from closing.
• Ensuring drivers are correctly trained in coupling and uncoupling, and the importance of the safety interlock being engaged.
• Considering a 10 weekly independent inspection of the coupling equipment or following the manufacturer’s recommendations.
• Available technology in the cab can warn the driver if the coupling is open, including audible alarms.

Maintaining a Drawbar coupling involves several key principles to ensure its longevity and safe operation:

• Regular cleaning and lubrication: Clean and lubricate the coupling weekly. This helps prevent wear and tear and ensures smooth operation.
• Visual Inspections: Ensure daily visual inspections to check for deformations, cracks, or other damage. Pay special attention to the locking pin, drawbar, drawbar eye, drawbeam, endplates and guiding funnel. Follow the manufacturers guidelines.
• Wear Measurements: Regularly measure wear on the coupling equipment, including the bolt dimensions and wear plates. Use equipment such as wear gauges to ensure dimensions remain within the manufacturers specified limits.
• Functional Checks: Test the locking pin function and ensure it operates correctly. For remote-controlled couplings, check the indicator lights in the cab (red/open, green/ closed)