ISO/TS 18506:2014

TECHNICAL ISO/TS
SPECIFICATION 18506
First edition
2014-03-01
Procedure to construct injury risk
curves for the evaluation of road user
protection in crash tests
Procédure de construction des courbes de risques pour l’évaluation de
la protection des usagers de la route dans les essais de choc
Reference number
ISO/TS 18506:2014(E)
©
ISO 2014

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ISO/TS 18506:2014(E)

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ii © ISO 2014 – All rights reserved

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ISO/TS 18506:2014(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Terms and definitions . 1
3 Methodology . 2
3.1 General . 2
3.2 Collect the relevant data . 2
3.3 Assign the censoring status . 2
3.4 Check for single injury mechanism . 2
3.5 Estimate the coefficients . 3
3.6 Identify overly influential observations . 3
3.7 Check the distribution assumption . 3
3.8 Choose the best distribution . 3
3.9 Check the validity of the prediction . 3
3.10 95 % confidence intervals and its relative size . 4
3.11 Quality index . 4
3.12 Recommendation of the injury risk curves . 4
4 Related electronic documents . 5
Bibliography . 6
© ISO 2014 – All rights reserved iii

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ISO/TS 18506:2014(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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on the ISO list of patent declarations received (see www.iso.org/patents).
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For an explanation on the meaning of ISO specific terms and expressions related to conformity
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 12, Passive
safety crash protection systems.
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TECHNICAL SPECIFICATION ISO/TS 18506:2014(E)
Procedure to construct injury risk curves for the
evaluation of road user protection in crash tests
1 Scope
The aim of this Technical Specification is to provide a procedure to develop injury risk curves for
biomechanical samples. These samples are often heavily censored and limited in size, such that specific
steps and checks are required when developing injury risk curves. Moreover, several statistical methods
were historically used to build injury risk curves. The curves resulting from the different methods could
be rather close or fairly different, depending on the biomechanical samples. It is therefore of major
importance to recommend a consensual method to be used. Otherwise, injury thresholds candidates to
be included into regulations could be highly influenced by the statistical method used. These different
[10]
methods were compared in a statistical simulation study . The conclusions of this study were used to
recommend the survival analysis.
This Technical Specification identifies steps to be followed to develop injury risk curves. It recommends
preliminary checks, statistical method, and recommendation process of the injury risk curve. Guidelines
on the type of the samples to be used (cadaver, animal, or dummy), as well as the variables to be used,
and the injury severity level are beyond the scope of this Technical Specification.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
injury risk curve
curve giving the probability, for a defined population and for a given input, to sustain a specified severity
of injury
2.2
injury risk function
mathematical function that relates a value of an injury criterion and possible additional factors
(variables) to a risk of sustaining an injury of a certain level
2.3
injury criterion
physical parameter which correlates well with a scale of injury severity of the body region under
consideration
2.4
injury value
value of an injury criterion
2.5
injury mechanism
mechanical behavior leading to an injury
2.6
abbreviated injury scale
AIS
scale allowing for the classification of injury severity
2.7
variable
parameters which contribute to the prediction of the injury severity
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ISO/TS 18506:2014(E)

3 Methodology
3.1 General
An injury risk curve corresponds to a statistical modelling of biomechanical data in order to predict the
risk of injury. Some general steps are required, as for any statistical model. The modelling includes the
choice of the variables to be used in the model. The choice of the model is also of major importance. Once
done, the variables of the model are estimated. Essential further steps are to check the assumptions of
the model and evaluate the model fit relative to the data used. The prediction is finally made possible
when the checks are done.
3.2 Collect the relevant data
The first step is to collect the relevant data, including injury types and severities, and injury values
measured during the tests.
There is no specification for the injury severity level (AIS ≥2, AIS ≥3) or the type of injuries evaluated
(fracture, soft tissue contusion, etc.).
The data could also include variables such as the Post Mortem Human Subject (PHMS) characteristics
(age, bone mineral content, gender, etc.).
The choice of the variables to be included in the construction of the injury risk curves is out of the
scope of the guidelines. The researcher’s expertise should guide this decision and is expected to vary
depending on the body region and injury mechanism considered.
3.3 Assign the censoring status
Once the biomechanical data are available, the censoring status must be assigned (left, right, interval
censored, exact).
Data are left-censored or right-censored if the measured injury value is greater than or less than the
injury threshold, respectively. The injury threshold is the minimum value that is associated with the
occurrence of injury for that subject. Data are interval-censored when the injury threshold is bounded
within a known range of injury values.
The censoring status can be provided by a coding which might differ from one statisti
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