Unformatted text preview: Week 11 Lecture B SAFE IS NOT A FOUR LETTER
Week 11 Lecture B ENG 1P03 2011 1 Which of the following are
mentioned in the PEO Code of
All of the above
None of the above Week 11 Lecture B ENG 1P03 2011 2 Introduction to Health & Safety
• “Regard the practitioner’s duty to the public
welfare a paramount”
• “Engineers may be responsible for managing
situations that contain potential danger for
those present or those who will occupy or
use the result of the work.”
• Failure to correct potentially dangerous
situations or failure to follow codes and
standards is professional misconduct.
Week 11 Lecture B ENG 1P03 2011 3 Safety in Design
• Design decision: decide between two
passenger car brake systems:
A. Lower cost; less safe
B. Higher cost; more safe • Safety measured by stopping distance
• Stopping distance correlates strongly
with severity of accident and injury Week 11 Lecture B ENG 1P03 2011 4 Questions
1. Is it ethical to recommend the lower cost
2. If yes, how do you reconcile this with the
Professional Engineer’s duty to the
3. If no, are all the Professional Engineers
who design less safe products acting
Week 11 Lecture B ENG 1P03 2011 5 Ford Pinto
Week 11 Lecture B ENG 1P03 2011 6 The Context
• The Japanese vs. the Americans
• No American car with less than six
• Should or should not Ford compete with
imports for the sub-compact market? Week 11 Lecture B ENG 1P03 2011 7 Lee Iacocca
• Born to Italian
• Trained as an
• President of Ford
• CEO of Chrysler Week 11 Lecture B ENG 1P03 2011 8 The Directive
• “The Pinto was not weigh an ounce over
2,000 pounds and not cost a cent over
$2,000.” Week 11 Lecture B ENG 1P03 2011 9 Week 11 Lecture B ENG 1P03 2011 10 Ford Pinto Controversies Week 11 Lecture B ENG 1P03 2011 11 Cost-Benefit Analysis
• Cost-Benefit Analysis
– Costs: $137,000,000
• Estimated as the costs of a production fix to all similarly designed cars
and trucks with the gas tank aft of the axle (12,500,000 vehicles ×
$11/vehicle) – Benefits: $49,530,000
• Estimated as the savings from preventing (180 projected deaths ×
$200,000/death) + (180 projected burn injuries × $67,000/injury) +
(2,100 burned cars × $700/car) • In 1970, the value of a human life was deemed to be
approximately $200,000 as a “cost to society” for each fatality
by the National Highway Traffic Safety Association (NHTSA,
an agency of the U.S. government).
• One Ford executive was quoted as saying
– “It's cheaper to let the customers burn.” Week 11 Lecture B ENG 1P03 2011 12 Role of Engineers in the Ford Pinto
Design and Production
• Engineers involved throughout, but in
– Crash testing
– Decision making with respect to design
adjustments to reduce negative outcome of
– Whistle-blowing Week 11 Lecture B ENG 1P03 2011 13 Questions
1. Did Ford do anything wrong?
2. Did Ford’s engineer’s do anything wrong?
3. What reason do you have to believe that
the Pinto was less safe than its
4. Was Ford just a victim of bad publicity? Week 11 Lecture B ENG 1P03 2011 14 Safety in Design
• Safety – “ The condition of being safe
from undergoing or causing hurt, injury,
• Risk – “ The possibility of loss or injury.”
• No such thing as absolutely safe.
• Acceptable Risk – A level of risk at which
the benefits are judged to outweigh
potential loss or injury.
Week 11 Lecture B ENG 1P03 2011 15 Constant Risk
r risk pc=r
log(p) + log(c) = log(r) Event probability p High Risk Low Risk r = 100
r = 10-2 c Event cost ($)
Week 11 Lecture B ENG 1P03 2011 16 i>clicker Question Event probability Which of the following statement is true?
A. C is riskier than A
B. C is more costly than D
C. D is more likely B
D. B is riskier than D
E. None of the above
C A D
c Event cost ($)
Week 11 Lecture B ENG 1P03 2011 17 Ford Pinto Discussion
• Any questions about the Ford Pinto and its story?
• What really bothered you about the discussion?
• What is your opinion on how the engineers and
• How was safety evaluated?
• Why did Ford get sued if they didn’t break any
laws and acted competently?
• How did engineers miss such an obvious
interaction between the bolts on the differential
and the fuel tank?
Week 11 Lecture B ENG 1P03 2011 18 Ford Pinto Discussion
• How does the public ascertain safety?
• Was the Pinto more or less safe than its
• Was the Pinto safe enough?
• What are mechanisms in place to ascertain
– The Profession
– The markets • What should have happened?
Week 11 Lecture B ENG 1P03 2011 19 Brake System Scenario
• Design decision: decide between two passenger car
A. Lower cost; less safe
B. Higher cost; more safe • Safety measured by stopping distance
• Stopping distance correlates strongly with severity of
accident and injury
• Under what conditions is it ethical to recommend the
lower cost system?
• Can safety be evaluate only by technical measures?
• Safety factor Week 11 Lecture B ENG 1P03 2011 20 The Maximalist Approach to Safety
• Minimalist approach
– Safety responsibilities
– Guidelines and principles for recognizing and
– Applicable safety codes and standards • Maximalist approach
– How do you make a safer car?
– How do you lead with ethics/values rather
than be constrained by them?
Week 11 Lecture B ENG 1P03 2011 21 Volvo’s Safety Concept Car (SCC) Week 11 Lecture B ENG 1P03 2011 22 Week 11 Lecture B ENG 1P03 2011 23 Week 11 Lecture B ENG 1P03 2011 24 SCC Design Features
• See-through A-pillars
• “Invisible” B-pillars
• Active rear-view
• Adaptive headlights
• Night vision Week 11 Lecture B • Collision warning
• Lane centring
• Flashing brake lights
• Four-point safety
belts ENG 1P03 2011 25 Week 11 Lecture B ENG 1P03 2011 26 ABS
• A major safety advance for automobiles
• First entered public consciousness through
advertising in the late 1980’s and 1990’s
• Daimler-Benz took credit for move of the
• “Daimler claimed that the invention was
driven so clearly by its interest in public
safety that the corporation would not pursue
any patent infringement suits over its
Week 11 Lecture B ENG 1P03 2011 27 ABS
• Advertising suggested this was
engineering design based on corporate
• The opposite is closer to the truth. It took
over 25 years of the work of a community
of engineers and many dead-ends before
the vision turned into an affordable,
Week 11 Lecture B ENG 1P03 2011 28 ABS
• It is an example of good design:
– It’s function is easy to understand.
– It is socially desirable.
– It works. • “The problem at hand and the community
addressing it were defined and evolved
simultaneously.” Week 11 Lecture B ENG 1P03 2011 29 ABS
• Initially a community of 50 researchers and
design engineers formed around the problem of
skidding automobiles. They met in 1958.
• There was no solution.
• They proposed many alternatives such as brake
distribution, disc brake systems, self-energizing
systems, hydraulic systems, etc.
• The British Road Research Laboratory (RRL) had
discovered that skidding caused a significant
number of accidents: about 27% of all accidents
on roads in 1957.
Week 11 Lecture B ENG 1P03 2011 30 ABS
• Lister adapted the first device from an
aircraft. Results were disappointing. The
distance the car took to stop was much
longer. Braking efficiency was too low.
• Dunlop developed another attempt device
that was prohibitively expensive and didn’t
reduce the stopping distance.
• A third device was design using an electronic
control module that could detect of calculate
the angular deceleration.
Week 11 Lecture B ENG 1P03 2011 31 ABS
• Teldix changed the problem from reacting to
wheel lock-up to regulating the braking. The
idea was to detect and regular imminent
• They added another criterion: it had to
reduce stopping distance on both wet and
• Siemens and American Microsystems jointed
the community by contributing paper at
conferences on the use of purpose-design,
solid state microprocessors in cars.
Week 11 Lecture B ENG 1P03 2011 32 ABS
• Most ABS in the 60’s and 70’s were
developed in partnership between a brake
producer and automobile manufacturer:
– Kelsey-Hayes & Chrysler
Alfred Teves with BMW
Benedix-DBS with Citroën
Teldex with Daimler-Benz • By the end of 80’s manufacturers were solid
on the idea
Week 11 Lecture B ENG 1P03 2011 33 ABS
• A June 1999 National Highway Traffic Safety
Administration (NHTSA) study found that
ABS increased stopping distances on loose
gravel by an average of 22%.
• A 2003 Australian study by Monash
University Accident Research Centre found
– Reduced the risk of multiple vehicle crashes by
– Reduced the risk of run-off-road crashes by 35%
Week 11 Lecture B ENG 1P03 2011 34 Week 11 Lecture B ENG 1P03 2011 35 Week 11 Lecture B ENG 1P03 2011 36 ABS Effectiveness
ABS improves steering control during rapid
deceleration especially on slippery road
ABS shortens the stopping distance, if
braking efficiency is high enough, because
on most surfaces static friction is greater
than kinematic friction.
Week 11 Lecture B ENG 1P03 2011 37 Munich Taxicab ABS Study
• Munich taxi fleet
• Taxis were all same make and identical in all
• Majority of drivers randomly assigned and
remaining drivers rotated
• 747 accidents
– ABS cars under-represented in accidents in which
the car driver was culpable
– ABS cars over-represented in accidents in which the
cab driver was not at fault
– Accident severity was independent of presence of
Week 11 Lecture B ENG 1P03 2011 38 Munich Taxicab ABS Study 2
• Accelerators used to measure
acceleration and deceleration at 100 Hz
for a total 3276 hours of driving
• Extreme deceleration occurred more
often in cars with ABS Week 11 Lecture B ENG 1P03 2011 39 Munich Taxicab ABS Study 3
• Observers recorded driving style.
• Drivers of cabs with ABS made sharper turns
in curves, were less accurate in their laneholding behaviour, proceeded at a shorter
forward sight distance, made more poorly
adjusted merging manoeuvres and created
more “traffic conflicts”
• Compared with non-ABS cabs, ABS cabs
were driven faster
Week 11 Lecture B ENG 1P03 2011 40 Munich Taxicab ABS Study 4
• Analysis of accidents for the year
following the initial study saw no
difference in accident or severity rate but
ABS taxis had more accidents under
slippery driving conditions Week 11 Lecture B ENG 1P03 2011 41 Munich Taxicab ABS Study
1. Drivers utilized ABS to their advantage, but no
improvement in the accident loss per time unit
of exposure to traffic could be seen.
2. A reduction in the accident rate did occur when
the drivers’ target level of risk was reduced by
increasing their expected cost of risk behaviour.
Did ABS merely shift the risk instead of reducing it? Week 11 Lecture B ENG 1P03 2011 42 Risk Homeostasis Theory
In risk homeostasis theory, the hypothesis
called risk homeostasis suggests that
individuals have a set level of acceptable
risk. Reducing risk in one area will therefore
lead to a change in behaviour that
increases risk elsewhere so that the
individual’s level of acceptable risk remains
Week 11 Lecture B ENG 1P03 2011 43 Review
• Holding the welfare of the public
paramount is a solemn duty.
• Evaluating what is safe enough and
making something safe are two different
• Acceptable risk is key to the
understanding of safety.
• Importance of communicating risk.
Week 11 Lecture B ENG 1P03 2011 44 ...
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This note was uploaded on 12/11/2011 for the course ENG 1c03 taught by Professor Lee during the Spring '11 term at Adventista de las Antillas.
- Spring '11