presentation on stairs, ala national conference, oct 2015

Australia’s leading safety and ergonomics experts

w www.ergonomics.com.au t 03 9376 1844 f 03 9376 3124 e [email protected] p PO Box 27 Parkville VIC 3052 a 200 Mt Alexander Road Flemington VIC 3031 abn 17 617 943 485

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Falls on steps and stairs

2015 Australian Law Alliance national conference

Ted Dohrmann B.E. (mech&manuf) B.Comm GDip (ergonomics)

Engineer and Ergonomist

Dohrmann Consulting

www.ergonomics.com.au

Executive summary

Steps and stairs present a common fall risk. They are regulated in numerous aspects, and

are open to objective assessment. This paper outlines practical steps to better understand

contributing factors and to evaluate liability in slip and fall accidents on steps and stairs.

Falls on stairs are common, and often lead to serious injuries.

Falls on stairs are often complex: there are many different ways that they can come

about.

Identifying who is at fault usually requires quite careful investigation. The cause(s)

are not always obvious.

Many stair accidents can easily be prevented and solutions implemented at

minimal cost.

Ultimately, however, steps and stairs should be designed and built properly,

consistent with regulations and common practice, having regard for their purpose

and use.

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Stairs1 represent a series of barriers which a pedestrian has to cross to go from one level

to another.2 Falls on steps and stairs are regrettably common, and injuries suffered can

be both permanent and severe.

Unravelling the causes of a fall on stairs can be complicated - there are multiple possible

causes that can lead to a fall. Importantly, many stair accidents could have been easily

prevented and solutions implemented at minimal cost.

This paper addresses some of the basic checks that should be made and the insights, laws

and Codes which can then be used to put a solid base under liability arguments.

A falls-on-stairs checklist is provided at the end of the paper. It is intended to provide the

practitioner with guidance in what to look for and what to ask clients when a fall on stairs

has occurred.

Key stair terms

Total rise: the dimension from finished floor level to finished floor level.

Individual rise: the dimension from the top of tread to the top of the next tread

(total rise/no of risers).

Total going: the dimension from the front of the nosing overhang at the bottom of

the stair to the back of the last riser at the top of the stair.

Individual going: the dimension from the front of the nosing on one tread to the

front of the nosing on the next tread.

1 A stair is defined as a minimum of two steps, consistent with the definition of the National Construction Code. 2 This discussion on stair slips is an extract from Professional Safety, June 1982 (modified)


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Pitch line: a diagonal line going from the bottom to the top of the stairs touching all

the nosings.

Head room: measured from the obstacle to the pitch line.

Nosing overhang: overhang of the tread past the riser.

Newel post: a substantial post that the handrail goes into on the staircase - usually

90 x 90 mm, can be either left at full height, or cut short for a newel turning to fit

into.

Newel cap: sits on top of the newel post for decorative effect.

Spindle: also known as balusters, these go between the handrail and base rail to

stop stair users from falling through. These are usually 41x41 mm and are either

square (sometimes fluted), or turned.

Risers: vertical timber, usually 9 mm thick. These are not mandatory, and when

missing the stair is called an “open riser” staircase.

Treads: horizontal timber, usually 22 mm in thickness. Are usually made thicker

for open riser stairs.

String: routed out timber usually 220 mm in width and 32mm thick, treads and

risers are slotted in, the top section can be cut away to create a cut string stair

case.

Handrail: follows the staircase up, and is where people place their hands and is

grooved out for spindles to sit into.

Bottom rail: sits on top of the string of landing and is grooved out for spindles to sit

into.


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The main question – what exactly caused the fall?

Causation usually falls into one of three categories:

1. Slips occur when a person's foot loses traction with the stair surface. The most

common causes of slips are insufficiently slip-resistant tread surfaces (e.g., highly

polished, wet, worn carpet, smooth paint or greasy). “My feet went suddenly from

under me”.

2. Tripping occurs when a person unexpectedly catches their foot on part of the stairs.

In most instances, the objects people trip on are small and unobtrusive, such as

cracks in a step, or a small lip, or a damaged nosing.

3. Mis-stepping occurs when a person oversteps a step or otherwise doesn’t land one

of their feet on the next level as expected.

“It was dark and I couldn’t see the steps very well” or “I was descending the stairs and

suddenly lost my balance”. Clients may mistakenly describe as a “slip” an incident which

is actually a “trip” or even a “mis-step”.

Every slip, trip or mis-step demands assessment of the visual environment which the stair

user was confronted with. What could a person keeping a reasonable lookout see?

The checklist supplied at the end of this paper will assist with identifying which of the above

categories a given fall on stairs incident falls into.

Slips on stairs

Stair climbing and descent is a learnt skill which becomes “natural”, even “forgotten”.

Climbing a stair requires an unusual gait which produces a high rate of energy expenditure.

Accidents caused by slips on stairs usually occur as the bodyweight is being transferred

onto or from a foot at the beginning or end of the swing phase of the stair-climbing gait,

and it is at these two points that the horizontal component of force exerted between the

shoes and the stair surface has been shown to be greatest.

However, stair slips occur most frequently (and are generally more serious) during stair

descent. The descending slip that occurs during first foot contact is the most dangerous.

It occurs as the leading foot is lowered onto the next tread, when the bodyweight is thrown

forward and outward. The slip may result from misplacement of the foot on the next tread,

or it may result when there is insufficient frictional force between the foot and the step to

allow the required weight transfer to occur. The body can then be thrown off balance and,

since the bodyweight is already thrown forward in the swing phase of descent, a fall is likely

to follow. The person must then be sufficiently agile to recover from the slip, or a handrail

must be present which the user can seize. An unbroken fall in descent can easily be

extended for the length of the stairs and can result in serious injury.

A "toe-off" slip during descent may also occur. Again, bodyweight is being transferred and

sufficient frictional force is required to allow the transfer to occur smoothly. The body can

be thrown off balance if this smooth transfer is interrupted. However, at toe-off the centre

of gravity of the body is held back, so a toe-off slip will usually result in a backward or

sideways fall rather than a headlong fall down the stairs.


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During ascent, slip accidents usually occur due to the rear foot slipping during toe-off or

due to the leading foot tripping or being misplaced on the next riser. In either case, the

body is generally thrown forward onto the stairs.

Biomechanical analyses of slips during walking and stair climbing have determined the

critical points during the walking or climbing step when slippage is more likely to occur. At

these points, the foot's (and the body's) forward momentum must be controlled. The forces

opposing the foot's momentum are the frictional forces which act between the foot (or

shoe) and the walking surface.

Walking and stair climbing are also affected by what a person sees or thinks. For example,

it has been shown that people imagine a visually glossy floor to be slippery, even where

blindfold tests show that the glossy floor is physically no more slippery than the dull floor.

Simply believing that the surface is slippery will normally cause a person to walk on that

surface with an unnatural gait. This change in gait may result in a slip and fall, not due to

any inherent slipperiness in the floor surface, but because the user's muscles cannot

control and support them in this unnatural walking style. A slip and fall in this case is

precipitated by the user's "perceptual misinterpretation" of the glossy finish on the floor.

Where a slip has occurred some of the key facts to establish are:

1. Tread material.

2. Tread condition.

3. Nosing.

Nosing can be very important, because it is where a lot of the “stepping” load occurs.

Usually a formal slip test is required to definitively establish whether or not the stair surface

offered adequate traction in the circumstances.

Wet or dry stairs?

The likelihood of a slip occurring increases in the wet. Stairs likely to get wet must have a

suitable surface treatment, particularly along their noses.

From 1990 onwards the National Construction Code (“NCC”, formerly the Building Code

Australia) required step treads to simply have “a non-slip finish or an adequate non slip

tread” near the edge of the nosing.

This rather non-prescriptive requirement with respect to the standard of slip resistance

required on stairs was updated in 2014. From that time, the NCC has required steps to

have a minimum slip resistance classification of P3/R10, in accordance with Australian

Standard AS 4586: 2013 Slip resistance classification of new pedestrian surface

materials. This rating corresponds to results obtained from testing with a “Pendulum” or

equivalent device.

It is therefore important to know the age of the steps (or their last renovation/repair) in

order to employ the correct applicable building standard.

There are a number of further slip resistance standards which may be applied to step

surfaces on stairs. One is AS/NZS 4663: 2004, AS 4663 2013 - Slip resistance

measurement of existing pedestrian surfaces. This standard assesses floor test results


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according to the “minimum notional risk of the surface contributing to a fall”, based on a

measured level of dynamic coefficient of friction, µ (pronounced “mu”).

HB197 1999 An Introductory Guide to the Slip Resistance of Pedestrian Surface

Materials.

HB198 2014 Guide to the specification and testing of slip resistance of pedestrian

surfaces.

The relevant handbook defines which slip resistance range should apply to the surface in

question.

The dynamic coefficient of friction (µ) is found using a suitable slip resistance test device

– typically either a SlipAlert or a Pendulum. The SlipAlert (pictured below) comprises of a

cart with a rubber pad underneath which is allowed to run down a ramp and across the

surface of interest.

The distance that the cart travels across the floor before it stops is measured, and is

related to the coefficient of dynamic friction for the floor (via a British Pendulum Number).

A Stanley Pendulum test device obtains the same result by a slightly different means.


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There are sometimes practical issues in obtaining suitable slip resistance measurements

on stairs (i.e. having enough space to conduct the test). Where a test cannot be

undertaken, expert judgement alone must be relied on for assessment of the stair surface.

Trips

User expectations and perceptions are especially important in stair usage. Stair climbing

is a learned behaviour, strengthened through usage. Stairway accidents are often caused

by simple errors triggered by some irregularity or lack of uniformity in the design or

construction of the stairs. People learn to expect and to depend upon a uniform stair

construction.

Two examples of trip hazards on steps appear below:

1. Worn carpet – it can catch feet.

2. Weather strips positioned at the threshold of doors.

Mis-stepping due to stair dimensions

Dimensional non-compliance with stair design rules as set out in the National Construction

Code can lead to a mis-step and fall.

The main design rules which apply to stairs in most buildings are:

Going and risers must be “constant” throughout in one flight (i.e. a step to step

difference of no more than +/- 5 mm).

Risers must not have any openings that would allow a 125 mm diameter sphere to

pass through the treads.

There must not be more than 18 or less than 2 risers in one flight.

Step goings: minimum of 240 mm (private)/250 mm (public), and a maximum of

355 mm (both).

Step risers: minimum of 115 mm to a maximum of 190 mm.


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Steepness factor: defined as twice the sum of the riser + going. The result of that

calculation must fall within a set range.

There must be at least a single handrail on at least one side of the flight if it is under

two metres in width. For stairs over two metres in width, there must be a handrail

on both sides.

Handrails, when provided, must extend for the full stair length. The following

photograph shows a handrail that does not extend the full length of the stairs. A

stair user approaching in the dark – relying on the handhold - could be misled.

For some industrial situations, the relevant stair design standard is Australian Standard

AS 1657-2013 Fixed platforms, walkways, stairways and ladders - Design, construction

and installation. This standard sets out requirements “for the design, selection,

construction and installation of fixed platforms, walkways, stairways and ladders that are

intended to provide safe access to places used by operating, inspection, maintenance and

servicing personnel”.

Mis-stepping due to not seeing the step properly

Incidents on stairs frequently occur due to problems with the stair user not being able to

see and comprehend exactly what they are doing while ascending or descending stairs,

even when alert.

There are two main categories of lighting problem: that of not enough light (illuminance)

or that of insufficiently conspicuous step edges (i.e. a lack of contrast) (luminance).

Either situation can lead to a mis-judgement of where to put your foot, and a subsequent

fall.


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In low light conditions, the applicable lighting standards are usually taken from either the

AS 1680 Interior lighting set or from AS/NZS 1158 Lighting for roads and public spaces.

Illuminance is measured using a light meter, and reported in units of lux.

For luminance contrast, the applicable guidance can be taken from AS/NZS1428 Design

for access and mobility. Luminance tests are undertaken using a luminance meter, and

are reported in units of candela per square metre (cd/m2).

Below, left – showing a lack of visual contrast to the left, and remedied on the right.

[END


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Falls on stairs - preliminary checklist Questions to ask your client

The accident

Yes Comments

Did you:

Trip, or,

Lose traction underfoot, or

Miss your footing?

□

□

□

What exactly do you think caused the

fall?

NA

Was your accident caused by:

Steep stairs, or

Inconsistent step size, or

Slippery stairs, or,

Other?

□

□

□

□

Where were you walking to and from?

NA

Had you been there before? If so how

often?

□

Yes Comments

Were you walking:

Up, or,

down

□

□


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the stairs?

Which part of the stairs had you

reached when you fell?

NA

Which way did you fall?

Backwards, or,

Forwards, or,

Sideways?

□

□

□

Do the stairs on which you fell on have:

Inadequate foot space on the

treads?

Steps of varying height?

Steps with excessive radius

(rounding) on the nosing (step

edges)?

□

□

□

Do the stairs consist only of a single

step?

□

Was there a handrail? How high was it? □

Were you using any handrails (if there

was one available)?

□


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Slips on stairs

Yes Comments

Was the stair surface:

Rough, or

Smooth?

And was the stair surface in:

Good or

Poor?

condition?

□

□

□

□

Which exact part of the step did your

foot slip on?

The tread.

The step edge (“nose”)

□

□

If the stairs were outside, or close to

outside, then what were the weather

conditions around the time of your

accident?

NA

Was the surface where you fell:

Wet, or

Dry?

□

□

If you slipped on the nose, was there

any anti-slip treatment applied to it?

□

For carpeted steps:

Was the carpet securely

attached to the stairs?

Was the carpet worn?

□

□


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Yes Comments

If wet, how did the surface get wet (e.g.

weather or spill)?

NA

Apart from water, was the surface

otherwise clean? E.g. oil, dust, powder.

□

Are the stairs covered?

□

Visual

Where exactly were you looking at the

instant that you lost balance and fell?

NA

Was there anything blocking your vision

of the way ahead?

□

What is the state of your vision?

Excellent.

Good.

Average.

Poor.

Do you wear glasses (and what for)?

Were you wearing glasses at the time?

□

□

□

□

□

□

If it happened at night, were the stairs lit

properly?

NA

Were the step edges (noses) clearly

defined? □


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Yes Comments

Were there shadows (including your

own) in front of you? □

Have you just moved from the dark into

the light, or vice versa?

□

Behavioural

Was there anything unusual about your

gait (that is, how you were walking)?

□

Were you:

Hurrying, or

Walking at a normal pace?

□

□

Were you carrying anything?

□

If you were carrying anything, how were

you carrying it? (E.g. in front of yourself,

in one hand, across the shoulder etc.)

NA

Were you on your own?

□

What footwear were you wearing?

NA

Was your footwear worn, and what was

its condition – especially the sole?

□

Do you still have the shoes that you

were wearing at the time of the

accident?

□

Prior to the accident, had you consumed

any alcohol, medicine or drugs likely to

have affected your gait, balance or

vision?

□


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Yes Comments

Do you have any medical history of

fainting or dizziness?

□

Was there any crowding or a need to

negotiate your way around other people

on the stairs?

□

[END

presentation on stairs, ala national conference, oct 2015

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