Civil Engineering Reference
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0.001
Unacceptable
region
0.0001
ALARP
0.00001
0.000001
Acceptable
region
0.0000001
1
10
100
1000
10 000
Fatalities (
N
)
6.3
Societal risk criteria.
Life quality index
The life quality index (LQI) is a compound social indicator proposed by
Nathwani
et al.
(1997), and can be used to evaluate the societal acceptability
of involuntary risk and to make cost-effective risk management decisions
related to life-safety. The LQI criterion shares a similar foundation with the
willingness-to-pay approach for increased survival (Shepard and Zeck-
hauser 1984), and has been successfully applied in establishing the accept-
able expenditure related to life-saving interventions (Pandey and Nathwani
2004; Rackwitz
et al.
2005).
The societal LQI,
L
, can be expressed as function of two measures of
public welfare, social wealth
G
and longevity
E
(Pandey and Nathwani 2004;
Rackwitz
et al.
2005):
(
)
ww
1
−
LG
=
E
[6.9]
where
G
is the consumption available in a unit of time;
w
is the fraction of
time allocated for economic activities and typically ranges from 0.12 to 0.20
for developed countries; and
E
is the age-averaged discounted life expec-
tancy of the population (Rackwitz
et al.
2005). If the societal LQI is dis-
cussed at a national level,
G
is often considered as a fraction of the gross
domestic product (GDP) per year and per capita. Note that the ratio
w
refl ects the national productivity and may change over time. Furthermore,
the societal LQI can be interpreted as a multi-attribute utility function cali-
brated for the general public, since
L
consists of a concave function of
G
with respect to
w
/(1
1 and a linear function of
E
. In other words,
under the defi nition of the societal LQI, the general public is considered to
−
w
)
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