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Climbing To Safety

Published: 04th Sep 2013 in OSA Magazine

Ergonomic and technological inroads into safe ladder use

In what is thought to be the first study of its kind on ladder design and use, Carl Sachs shares its details and conclusions with readers. This follows the excellent feedback he received at the recent ISFP (International Society for Fall Protection) Conference in Las Vegas.

It is one thing to design a ladder so it won’t fall off a skyscraper and something else entirely to design the ladder so the person using it won’t fall off. But for too long, we have confused the two, accepting safety standards that concentrate on the structural integrity of equipment without considering their human users. 

Australia’s biggest selling safety standard of all time, AS1657 Fixed platforms, walkways, stairways and ladders – Design, construction and installation, is, sadly, a perfect example of this oversight. 

It’s also a very dated standard and as a member of the committee responsible for its first revision in 20 years, I was shocked to discover the committee was forced to make critical judgements in an information vacuum.

To be fair, we had plenty of evidence to guarantee structural integrity: a ladder built in compliance with AS1657 will not buckle, break or collapse. But when it came to the safety of the user, there was almost no evidence. And no budget to gather it, either.

I was so concerned that many of the standard’s recommendations were based purely on opinion, thatI commissioned exploratory research by prominent ergonomist, Professor David Caple. 

His report found it was possible to design a ladder that was more comfortable for users without violating the existing standard, with potentially life saving advantages.

“Some of the issues that have come out of this study could be deemed to be life saving if the behaviours that we saw could be repeated in a larger study, using a broader section of the population,” Professor Caple said. “If those behaviours are indicative, then we have found some risks that do need to be addressed.”

The Caple study analysed video footage of Australians using ladders. It investigated how aspects of the draft revised AS1657 standard affects various body types from an ergonomic perspective.

Importance of Australian Standards

Australian workplace health and safety law demands workplaces do whatever is “reasonably practicable” to control hazards. Australian Standards are regarded as evidence of what is reasonably practicable to implement in a workplace and may be referenced in law. 

AS1657 is referenced in the National Construction Code, previously the Building Code of Australia, and the national fall prevention code of practise. It is an important standard and widely used in industry. Of the 20,000 standards published by SAI Global, it’s the fifth highest selling standard and the number one safety standard.*

Each standard represents the collective knowledge and expertise of experts in the field. The AS1657 committee represents the regulators, the Australian Building Codes Board, Master Builders, safety associations and user groups.

All of these associations and representatives donate their time to writing, research, and meetings. Standards Australia’s function is purely administrative: arranging meetings, distributing updated versions, editing and circulating the standard for public comment. 

A group of volunteers with no budget, the committee has limited access to do practical research or studies. Instead, the committee draws on its experience.

How the study worked

Three types of ladders were set up, including a:
• Step type ladder
• 70-degree rung ladder
• Vertical rung ladder

Two ladders in each of the three categories were set up with different features to observe the difference between ladders of the same type. 

A random selection of candidates climbed up and down the ladders numerous times and were observed and filmed.

The footage was analysed by Professor Caple, who made observations and recommendations as part of a dynamic risk assessment.

*According to their website listing of top selling standards.

The research paper compares:
• The current AS1657 standard
• The study’s findings
• Recommendations
• The draft revised AS1657 standard

Caple research findings

1. The best ladder type
All the ladder users in Professor Caple’s study expressed a preference for the step type ladder. (In North America, these are known as ‘ship ladders’). Second was the 70-degree rung ladder, while the vertical ladder was the least popular. 

Users said they felt more secure and stable using the hand rails on the step type ladder, and maintaining their three points of contact on this option. 

Professor Caple explained that the step type ladder shifts the load onto the legs for climbing and hands simply help with balance. 

The 70-degree rung ladder also shifts the load to the legs but, due to the circular rung profile, climbers make greater use of their hands for support while climbing up and down.

In contrast, vertical ladders force users to rely on upper body strength to climb up and down the ladder, which is far more tiring.

Are step type ladders affordable? A step type ladder costs about ten percent more than a rung type ladder, but there are operational savings. 

A person can climb the step ladder holding a tool box or other lightweight item (say 10kg) and still maintain three points of contact due to the uninterrupted hand-hold. 

This is impossible on the rung type ladder since the rungs or stiles act as the hand-hold point. Because rung ladder users must let go with one hand and replace it with the other to maintain three points of contact, they cannot carry anything in one hand. 

After allowing for the cost of shifting the same 10kg load by other mechanical means or roping it up safely, the overall cost of the step ladder is significantly less than the rung type – a safer option, and much more likely to be used correctly rather than relying on people roping up equipment. 

2. Inter-tread spacing on step ladders
Two step ladders were involved in the study: one with steps spaced approximately 215mm apart and one at 250mm spacings. 

Professor Caple observed that the 250mm spacing suits the natural gait better than 215mm spacings. A distance of 300mm was also comfortable for all subjects, irrespective of their height or shape. Modelling confirmed uniform 250 to 300mm spacings would work in a variety of ladder heights. 

The increased spacing is likely to require fewer treads, resulting in a lower overall cost for the step type ladder.

3. Top and bottom rung position on rung type ladders

Non-uniform spacings at the base and, sometimes, at the top of a ladder, tend to be created when standardised ladders are cut down to size on site rather than purpose-built. 

The Caple study warns, however, that a new hazard is created when the distance between the base of the ladder and the lowest rung is less than the spacings between the rungs on ‘cut to size’ ladders.

Users tended to miss poorly spaced bottom rungs altogether when climbing up the ladder. When climbing down the ladder, the subjects were looking at the face of the ladder, or upwards. Some of the subjects stumbled, their natural gait impeded, since they expected the last rung to the landing to be equal. 

At the top of the ladder, the user climbed over an unevenly placed top rung and searched around for the top rung while climbing down backwards. This was of particular concern, since this is at the highest point in the ladder.

The study recommended that rungs remain uniform throughout the ladder and that the top rung be level with the top landing platform, rather than one full rung below, since this presented a major safety issue. 

The need to fabricate ladders specifically to suit the site situation is unlikely to increase the overall cost of the equipment. The stiles and rungs of a ladder are a small portion of the overall cost of the complete system installation, e.g. brackets, cage, bottom and top landings, labour and fixings. The only issue may be that builders would need to plan ahead rather than rely on an off the shelf, cut to size item, just as they allow for the measure and installation of a staircase. 

4. Clearance behind step ladders
For users to quite literally get a ‘toe-hold’, Professor Caple recommends a minimum clearance of 100mm from the back of the ladder.

When the clearance was only 50mm, study subjects consistently hit the back structure with their feet. The problem was exacerbated at the second tread from the top, since this tread was closest to the rear wall. 

5. Transition from rung ladder to landing
The transition between the ladder and a landing deserves special attention, given the findings of the Caple study.

Two types of extended stiles were installed on the two vertical ladders. One had circular ‘D’ handrails that extended on to the landing and the other simply had vertical extended stiles.

When subjects climbed from the landing back down to the ladder, they felt behind them for the vertical upstands and had to contort their arms to gain a hand-hold. The circular rungs allowed them to achieve a grip before climbing back out to the ladder and to maintain the handhold all the way until they were comfortable and secure. 

This was the highest point in the ladder, so a fall from a height of three metres from the person’s feet would almost certainly result in a death or permanent disability. 

Professor Caple’s report concluded that “If they (ladder users) held onto the vertical stiles that extended over the landing, they stepped backwards from their centre of gravity to find the first rung. The less experienced appeared to be less confident in making this first step.

“There were evident potential fall risks occurring as they were trying to transition from the top rung of the ladder on and off the landing. 

“In particular, when they were transitioning off the landing on to the top rung, it was difficult for them to position their foot onto the rung while maintaining three points of contact with their hands on the styles and their other foot still on the landing. 

“Their centre of gravity was behind their hand position and they were looking down through their feet to try to see the top rung of the ladder.” 

Professor Caple recommends the stiles extend over the landing so users can stabilise their posture with their hands while they find the top rung with their feet. This is achieved with D-shaped handrails.

Workplace Access & Safety warns, however, that workplaces avoid welded handrails, which are prone to failure. 

6. Clearance between stile and handrail on step ladders
Getting the handrail right is important on step ladders, too.

“Where the hand rail was up to 250mm away from the treads, the subjects tended to have their elbows in line or behind their torso,” Professor Caple wrote. “They attempt to climb the stairs with a vertical posture, or even leaning back.”

Users were able to support a more stable vertical posture when the distance was 150mm.

7. Rung shape
Both the 70-degree and vertical rung ladders had semi-circular rungs that were approximately 50mm deep but the radius was either:
• 100mm at the top (the ‘rounder’ type)
• 250mm that was also about 50mm deep (the ‘flatter’ type)

The flatter rung provided much more stability. The subjects’ feet tended to roll over the rounder rung on the ‘cut to size’ ladder and their centres of gravity shifted further back. On the flatter rung, subjects were able to stand in a more upright position and maintain a more vertical posture.

Professor Caple recommends a flatter rung with a slightly rounded edge for a comfortable hand grip.

Conclusion

The message for the global fall prevention community from the Caple study is simple: the many small details that comprise good design – just a few millimetres here and there – can make an immeasurable difference to the lives of people who work at height. 

In itself this is a big leap forward in ladder safety. 

Published: 04th Sep 2013 in OSA Magazine

Author


Carl Sachs


Carl Sachs is the managing director and falls prevention specialist at Workplace Access & Safety, and takes an active role in the development of fall prevention standards. He represents the Master Builders Association on the committee for AS 1657 - 1992: Fixed platforms, walkways, stairways and ladders - Design, construction and installation.

Sachs is dedicated to building a general awareness of this highly specialised area of risk, training facility managers of major retail corporations and regularly addressing OHS professionals at national conferences.


carls@workplaceaccess.com.au
http://www.workplaceaccess.com.au

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