In the past, any design emphasis on ergonomics, occupant restraint against sudden

deceleration, and travel comfort had been poorly lacking. According to a study by Monash University’s Maintenance Technology Institute (MTI), many injuries in Bowen Basin mines relate directly to various features of personnel transport vehicles.

Most common short-term injuries are neck injuries due to the head hitting the cabin roof at bumps; back injuries; and ankle injuries caused when exiting the vehicles. Both short-term and long-term back injuries can be associated with jolts, jars and vibrations caused during travel, as well as poor ergonomic conditions of seating.

Restraints are also a problem, with current seatbelts identified as difficult and uncomfortable to wear and incorrectly positioned upon the body.

Exposure to vibration can lead to a range of health-related problems, including disorders of the joints and muscles, especially the spine, cardiovascular, respiratory, endocrine

and metabolic changes.

According to a paper presented at the Queensland Mining Industry Health & Safety Conference by Darrell Grant, Daya Dayawansa and Paul Curcio, cabin layout of vehicles used before the retro-fit project at Kestrel were basic, with little emphasis placed on safety, comfort and ergonomics.

The rear cabin consisted of two steel bench-style seats covered with foam cushions accommodating up to ten miners in a ‘troop carrier’ type configuration. Seating posture was poor with inadequate back support and insufficient head room increasing the risk of neck and back injuries. The style of seating without a suitable restraint system also didn’t protect passengers against sudden decelerations.

With this in mind, a project team was formed to completely retrofit a vehicle in 12 weeks in order to improve safety and comfort of operators and passengers during underground

personnel transport by providing ergonomically designed cabin layouts and seating with appropriate restraint systems, taking into account the size of people ‘kitted’ for work in

underground.

The project team was made up of project owners and end users from Kestrel, Monash University, Kade Development and Specialised Mining Vehicles (OEM). The end users were given a major role to play in specifying safety, comfort and other functional requirements, and the role of the OEM and the engineers in the team was to develop engineering solutions to accommodate them as best as practicable.

The key issues revolved around safety and comfort, vehicle weight and flexibility, and the designers were constrained by vehicle dimensions and ground clearance.

It was decided to extend the rear cabin to accommodate a total of 11 people. The final cabin layout required significant changes to the chassis to meet roof height requirements.

It was necessary to lower the floor level and hence the chassis by at least 150mm. As the chassis beams are subjected to very high levels of fatigue loading, the design for a welded beam had to be fully tested. A prototype was tested for stress and the welded chassis beams successfully passed tests.

The front cabin seats were provided by KAB seating and featured air suspension and lumber support adjustment and integrated head rest.

For the rear-seating plan, four of the nine rear seats had to be mounted over the wheel arches – making for major challenges in terms of ergonomic and suspension design of the seats. According to the paper’s authors, selection of the rear cabin seats was more difficult in terms of utilising suspension seating given the space limitations. A decision was taken to design and build a new seat. A prototype was designed by Monash University.

The seats were put through static proof load tests and a suspension mechanism was incorporated into the seat frames. The seat frame incorporated suspension, which made it possible to further reduce the shock and vibration level in rear seats.

A lap/sash with the 4N retractor, suitable for sprung seats and stainless steel aircraft buckle combination, was selected as the most suited commercially available restraint.

Rio Tinto Coal Australia commissioned VIPAC to conduct vibration measurements on one of the modified Driftrunners and compared them to a standard (non-modified) vehicle. Trials found the modified Driftrunner had about 32% less vibration to front and rear passengers, mainly due to less floor vibration. The sprung seats also offered a 33% reduction in shock impact.

Kestrel said end user acceptance of the new design had been good with favourable comments, especially about comfort levels. Feedback has also initiated further improvements, including improving seating suspension, increased legroom,

and reduction of rear cabin vibration levels.

The head rests on the rear seats were changed to improve driver rear visibility and the back four seats and centre seats were altered to fold up to increase storage room when the vehicle was not being used to transport people.

The team also managed to decrease the overall vehicle height down to 1960mm and still retained sufficient head clearance to meet the required 1000mm distance between seat pan and roof.

Based on the paper “Confronting a real underground safety issue – Improving safety and comfort in underground personnel transport” by Darrell Grant, Daya Dayawansa and Paul Curcio.