Unplanned Disengagement: Truck safety is of the utmost importance

Unplanned Disengagement: Truck safety is of the utmost importance

© Miguel Perfecti

Truck safety on the highway is a serious concern for the transportation industry, affecting not only the lives of drivers but also all road users. It is imperative that industry stakeholders prioritize and adhere to stringent safety measures. Drawing on over fifteen years of industry experience, TT Club’s Josh Finch delves into one aspect of truck safety that he sees repeatedly causes injury: unplanned breakaways.

An unplanned disconnection incident refers to the sudden and unexpected separation of the tractor unit from the trailer unit to which it is attached. This event may occur during transport on a public road, or, more commonly, in the transport yard after the coupling procedure has been completed. Such accidents have various causes, including mechanical failure, human error, or adverse road conditions.

Such accidents can have serious consequences, posing immediate danger to the vehicle driver and others nearby. The vehicle may be damaged, as well as the infrastructure of the transportation facility or road. In addition, there may be damage to the goods. Furthermore, these incidents impact operations, causing delays, schedule disruption, and costly downtime for trucking companies.

How accidents happen

In order to connect a tractor unit to a trailer, the driver aligns the trailer’s lead pin with the tractor’s fifth wheel. The main pin is a cylindrical steel pin located on the underside of the front of the trailer, while the fifth wheel is a horseshoe-shaped coupling device mounted on the back of the tractor. Normally, when the lead pin and fifth wheel are properly engaged, only extreme pressure causes the two to separate. However, there are several factors that may affect the coupling of the two units.

During the connection process, the jaw (a component of the fifth wheel) should grip the lead pin, but improperly maintained equipment can make it difficult for it to fully grip. In particular, if the grease used to cover the fifth wheel is too thick, it may cause the jaw to engage the main pin partially but not completely. Thick grease may also prevent the driver from seeing that the fifth wheel is operating incorrectly. If the jaw is partially engaged, vibration from the road, hard braking or load shifting may cause the fifth wheel to separate from the main pin.

In addition, drivers and operators should be aware that errors in the control pin and related components may cause failure. The main screw is connected to the container table under the trailer. If this connection fails, perhaps due to improper welding, the lead screw itself may fail. This rarely happens but the consequences can be disastrous.

TT Club

King Under Trailer

A related problem arises from the design of trailer braking systems that use air instead of hydraulic fluid, and are engaged when air is exhausted from the system. This design means that brake failure due to mechanical failure is very rare. However, it poses a risk to the person attaching the tractor unit to the trailer. If the trailer parking brake is not activated, the trailer brake may release unexpectedly when the air line is connected to the trailer during coupling and the trailer may roll. If it moves toward the tractor unit, it may trap the person making the connection between the tractor and the trailer, resulting in serious injury or death.

Planned preventive maintenance and pre-use checks

Strict pre-use inspections mitigate the risk of unplanned uncoupling, requiring drivers to carefully inspect the tractor-trailer combination beforehand. Proper training and adherence to this procedure ensures that any mechanical problems can be identified and addressed. Such comprehensive inspections prior to use, including yard use, must also be recorded and made available to demonstrate that remedial action has been taken.

Likewise, a planned preventative maintenance schedule ensures that all components, including the fifth wheel and brake systems, are in optimal working order and within the manufacturer’s operating tolerances, and that there is no grease buildup that may prevent effective coupling.

Although pre-use checks are important and will often highlight maintenance issues, due to the technical nature of some faults, there is no substitute for regular, rigorous inspection by a trained vehicle engineer. Most jurisdictions require that heavy goods vehicles undergo regular preventive maintenance and operators must be familiar with the requirements in certain areas.

Furthermore, effective information management will maximize the opportunity for fleet managers to make smart purchasing choices and provide feedback to vehicle manufacturers, as well as enable safety enhancement, such as monitoring common faults and defects, and taking proactive actions to prevent future breakdowns. .

How actions can help

Proper driver actions are essential to safety, providing drivers the opportunity to not only identify defects, but also ensure that the tractor and trailer are coupled safely and correctly. Careful steps must be in place that include aligning the lead pin with the fifth wheel, lowering the landing gear, operating the locking mechanism, and ensuring the safety chain is properly engaged. During these procedures, drivers should ensure that the parking brakes on both the tractor and trailer are engaged when the vehicle is not being driven. After engaging the fifth wheel and main clutch, but before connecting the air line, the driver should test the pair by selecting a low gear, with the trailer brakes still engaged, and pulling slowly forward.

Training in such procedures should be provided to all participants to reduce the risk of human error. It is recommended that special attention be paid to shifters or yard workers responsible for moving trailers within a transfer station or yard, who may couple and disengage dozens of times each day and may not be fully qualified heavy goods vehicle drivers.

More importantly, with the incorporation of new safety technologies, such as automatic locking systems and key sensors, special care is needed. Be aware that new equipment or modified technology may result in fleets with different safety features or protocols. This can be confusing; Training systems should take into account all vehicles used within the fleet, including rented or temporarily rented vehicles.

The importance of safety culture

A cultural focus on safety reinforces the importance of following established procedures at all times and empowers the workforce to make decisions that enhance the safety of themselves and others.

The temporary nature of the driving workforce often makes this difficult; Ensure that all drivers, including temporary drivers and sub-contractors, are held to the same high standard and that this standard is held through rigorous training and assessment, and is demonstrated by management commitment.

In-depth reading: Coupling and decoupling – transfer in the workplace (hse.gov.uk)

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