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NURUL IKHMAR IBRAHIM SCHOOL OF MANUFACTURING ENGINEERING
UNIMAP
DESIGN FOR SAFETY
Course Outcome
CO 3: Ability to analyze and
evaluate products’ safety
using suitable methods.
Today’s topic
Safety Definition Designing Safe
Products
Safety Problems &
Human Failures
In Malaysia , home is second to road as a place
for injury morbidity and mortality. There were 13,401
home injury cases and of which 44 cases (0.3%) were
fatal.
Products such as floor and flooring surface, stairs,
furniture, toys and baby walkers had been identified
as factors that could contribute to injury.
Source: Hasni, H., Junainah S. and Jamaliah J., 2003, Epidemiology of
Home Injury in Malaysia
SAFETY DEFINITION
WHY? PRODUCTS ARE UNSAFE TO USE
SAFETY DEFINITION
Most product safety problems
arise from improper product use
rather than product defects.
THOMAS A. HUNTER
SAFETY IS FREEDOM FROM
DANGER, INJURY OR DAMAGE
HARM
Physical injury or damage
to the health of people or
damage to property or the
environment.
[ISO/IEC Guide 51:1999, definition 3.3]
SAFETY DEFINITION
HAZARD
Potential source of harm.
[ISO/IEC Guide 51:1999, definition 3.5]
SAFETY DEFINITION
ERGONOMICS HAZARD
In terms of users’ mental &
physical capabilities, which
include:
1. Body dimension.
2. Strength & posture.
3. Frequency, duration &
intensity of task/work.
4. Information processing
(Human error)
5. Environmental factors
SAFETY DEFINITION
RISK
Combination of the
probability of occurrence of
harm and the severity of
that harm.
[ISO/IEC Guide 51:1999, definition 3.2]
SAFETY DEFINITION
DANGER
A combination of risk and
probable hazard
consequences.
SAFETY DEFINITION
Today’s topic
Safety Definition Designing Safe
Products
Safety Problems &
Human Failures
INFLUENCES OF CONSUMER SAFETY m
icro
m
ac
ro
SAFETY INFORMATION
Government Standards Industry
Consumer behaviour Conditions of use
PRODUCT
DESIGN
CONSUMER SAFETY
People can cause or contribute to
accidents – human failures.
THERE ARE 2 CAUSES OF
HUMAN FAILURES
THERE ARE 2 CAUSES OF
HUMAN FAILURES
VIOLATIONS ERRORS + INJURY, DEATH & DAMAGE =
HUMAN ERROR IS THE FAILURE
OF PLANNED ACTIONS TO
ACHIEVED THEIR DESIRED
NEEDS
It is suggest that human error is a
primary cause of 60-90% major
accidents.
There are 2 basic types of
human error:
1.Skill-based error
2.Mistakes
HUMAN ERRORS
Skill-based error
Involve routine tasks in familiar
situations.
May cause by inattention or
over attention.
Two categories – slips and
lapses
HUMAN ERRORS
Slips
Failure of execution of planned
tasks i.e. ‘action-not as-
planned’.
May be due to distraction from
task or preoccupation with other
things.
SKILL-BASED ERROR
Slips – examples
Picking up the wrong
component from a mixed box.
Omitting a step or series of
steps from a task.
Performing the action in the
wrong direction (e.g. turning a
control knob to the right rather
than the left.
SKILL-BASED ERROR
Lapses
Failures to carry out an action
due to forgetfulness (memory
failures).
Can be reduced by minimising
distractions and interruptions to
tasks and by providing effective
reminders.
SKILL-BASED ERROR
Lapses – example
SKILL-BASED ERROR
Mistakes
Do the wrong thing believing it
to be right.
Two types of mistakes – rule-
based and knowledge-based.
HUMAN ERRORS
Rule-based mistakes
Occur when our behaviour is
based on remembered rules or
familiar procedures.
It is called rule-based because
we apply rules of the kind: if
(this situation) then do (these
actions).
MISTAKES
Rule-based mistakes -
example
MISTAKES
Knowledge-based
mistakes
May occur when we have to
think our way through a novel
situation for which we do not
have a procedure or “rule”.
Make wrong judgement due to
insufficient knowledge or
experience (lack of expertise).
MISTAKES
Knowledge-based
mistakes - example
MISTAKES
VIOLATIONS ARE ANY
DELIBERATE DEVIATIONS FROM
RULES, PROCEDURES,
INSTRUCTIONS & REGULATIONS
There are 3 categories of
violations:
1.Routine
2.Situational
3.Exceptional
HUMAN ERRORS
Routine
Breaking the rule or procedure
has become a normal way of
working within the work group.
VIOLATIONS
Routine - example
VIOLATIONS
Situational
Breaking the rule is due to
pressures from the job such as
being under time pressure, the
right equipment not being
available, or even extreme
weather conditions.
VIOLATIONS
Situational – design features which increase
violation
VIOLATIONS
Situational - example
VIOLATIONS
Exceptional
Rarely happen and only then
when something has gone
wrong.
VIOLATIONS
Exceptional - example
VIOLATIONS
Today’s topic
Safety Definition Designing Safe
Products
Safety Problems &
Human Failures
SAFE PRODUCT DESIGN CAN BE
ACHIEVED VIA 3 COMBINED
APPROACHES
Intrinsic Safety
Focused on immediate/initial
use.
Minimizes direct injury from
device (e.g. sharps, burns)
DESIGNING FOR SAFETY
Ergonomic Safety
Focused on repetitive and/or
long-term use.
Minimizes fatigue and
cumulative injury effects (e.g.
carpal tunnel)
DESIGNING FOR SAFETY
Usable Safety
Focused on full life-space of
product use.
Minimizes opportunities for
incorrect use (e.g. overdose)
DESIGNING FOR SAFETY
SAFE PRODUCTS CAN BE
DESIGNED THROUGH ERGONOMICS
EVALUATION METHOD
What should you
evaluate?
The features of the product.
DESIGNING FOR SAFETY
#1
What should you
evaluate?
The physical and psychological
characteristics of the user.
DESIGNING FOR SAFETY
#2
What should you
evaluate?
How the product will be used,
associated with tasks and
activities.
DESIGNING FOR SAFETY
#3
What should you
evaluate?
Environmental factors.
DESIGNING FOR SAFETY
#4
The evaluation must consider
all stages of product’s
lifecycle.
A
FRAMEWORK
FOR
PRODUCT
EVALUATION
PROCESS
Some useful guidelines:
Designer must avoid any design which expects
or requires individual/users to:
Exceed their physical strength.
Perform too many functions simultaneously.
Detect and process more information than is possible.
Perform meticulous task under difficult environmental
conditions.
Work at peak performance for long periods.
Work with tools in cramped spaces, etc.
EXAMPLES OF EVERYDAY
PRODUCTS
Figure 1 : Labelling around the
programme control is difficult to
read
Figure 2 : Protruding dials are
easy to grip and the labelling
easy to see
A B C
Figure 3 : Interface design of microwave ovens. Design A combines
simplicity and functionality. Design B and C leads to confusion and
many user errors
Figure 4 : Switches which are identical in shape and arranged in one-
dimensional row make it more possible to commit error. There are two
solutions: place a visual display with the switches (A) or arrange the
switches to match the room layout (B)
A B
Figure 5 : Which control goes to
which burner?
Figure 6 : Full natural mapping of controls and burners
Figure 7 : A typical power
plant control room
Figure 8 : Make the controls look and
feel different. The control-room
operators in a nuclear power plant tried to
over come the problem similar-looking
knobs by placing beer-keg handles over
them
Make sure that the user can
figure out what to do!
Make sure that the user can tell
what is going on!
References
Ergonomics and Safety in Consumer Product Design, B.
Norris and J.R. Wilson in Human Factors in Product
Design: Current Practice and Future Trends. (2001)
Patrick W. Jordan and William S. Green
Rapid Alert System for non-food products posing a
serious risk (RAPEX).
http://ec.europa.eu/consumers/ipm/risk_assesment_guid
elines_non_food.pdf
Designing safety into products, Beverley Norris and John
R. Wilson
http://person.hst.aau.dk/pm/ab/DSP.pdf
References
MS ISO 12100:2012 Safety of machinery - General
principles for design - Risk assessment and risk
reduction