# ISO/TS 20459:2023

(Main)## Road vehicles — Injury risk functions for advanced pedestrian legform impactor (aPLI)

## Road vehicles — Injury risk functions for advanced pedestrian legform impactor (aPLI)

This document provides definitions, symbols and injury probability functions (IPFs) for the thigh, leg and knee intended to be used with the advanced pedestrian legform impactor (aPLI), a standardized pedestrian legform impactor with an upper mass for pedestrian subsystem testing of road vehicles. They are applicable to impact tests using the aPLI at 11,1 m/s involving: — vehicles of category M1, except vehicles with a maximum mass above 2 500 kg and which are derived from N1 category vehicles and where the driver’s position, the R-point, is either forward of the front axle or longitudinally rearwards of the front axle transverse centreline by a maximum of 1 100 mm; — vehicles of category N1, except where the driver’s position, the R-point, is either forward of the front axle or longitudinally rearwards of the front axle transverse centreline by maximum of 1 100 mm; — impacts to the bumper test area defined by References [1] and [2]; — pedestrian subsystem tests involving use of a legform for the purpose of evaluating compliance with vehicle safety standards.

## Véhicules routiers — Critères lésionnels et courbes de risques pour l'impacteur en forme de jambe de piéton (aPLI).

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TECHNICAL ISO/TS

SPECIFICATION 20459

First edition

2023-04

Road vehicles — Injury risk functions

for advanced pedestrian legform

impactor (aPLI)

Véhicules routiers — Critères lésionnels et courbes de risques pour

l'impacteur en forme de jambe de piéton (aPLI).

Reference number

ISO/TS 20459:2023(E)

© ISO 2023

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ISO/TS 20459:2023(E)

COPYRIGHT PROTECTED DOCUMENT

© ISO 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.

ISO copyright office

CP 401 • Ch. de Blandonnet 8

CH-1214 Vernier, Geneva

Phone: +41 22 749 01 11

Email: copyright@iso.org

Website: www.iso.org

Published in Switzerland

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ISO/TS 20459:2023(E)

Contents Page

Foreword .iv

Introduction .v

1 Scope . 1

2 Normative references . 1

3 Terms and definitions . 1

4 Symbols and abbreviated terms.3

4.1 Symbols . 3

4.2 Abbreviated terms . 4

5 IPFs for the aPLI . 4

5.1 General . 4

5.2 Thigh . . 6

5.3 Leg. 7

5.4 Knee . . 8

Annex A (informative) Rationale regarding background and methodology to develop IPFs

for the aPLI .11

Annex B (informative) Adjustment of IPFs for real-world relevance . 105

Annex C (informative) Supplemental data . 135

Annex D (informative) Influence of PMHS test data (dfbetas > 0,3) against IPFs for human . 136

Bibliography .154

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ISO/TS 20459:2023(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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 36,

Safety and impact testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.

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ISO/TS 20459:2023(E)

Introduction

This document has been prepared on the basis of the existing injury probability functions (IPFs) to be

used with the advanced pedestrian legform impactor (aPLI) standard build level B (SBL-B). The purpose

of this document is to document the IPFs for the aPLI in a form suitable and intended for worldwide

harmonized use.

In 2014, development of the aPLI hardware and associated IPFs started, with the aim of defining

a globally accepted next-generation pedestrian legform impactor with enhanced biofidelity and

injury assessment capability, along with its IPFs, suitable for harmonized use. Participating in the

development were research institutes, dummy and instrumentation manufacturers, governments, and

car manufacturers from around the world.

IPFs for the aPLI specified in this document predict injury probability to specific regions of the lower

limb of a pedestrian that corresponds to maximum values of injury metrics obtained by the aPLI in a

subsystem test, as described in References [1] and [2]. As the IPFs do not provide any threshold values,

users will need to determine target injury probability, based on their specific needs, to define injury

assessment reference values to be used for their test protocol.

It is also important to note that the subsystem test procedure (STP) for pedestrian protection may not

be representative of pedestrian accidents for specific injury metrics, depending on their sensitivity to

pedestrian impact conditions such as lower-limb posture and muscle tone. The IPFs for the aPLI have

been validated against accident data and some ideas to compensate for the discrepancy against accident

data are presented in Annex B.

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TECHNICAL SPECIFICATION ISO/TS 20459:2023(E)

Road vehicles — Injury risk functions for advanced

pedestrian legform impactor (aPLI)

1 Scope

This document provides definitions, symbols and injury probability functions (IPFs) for the thigh, leg

and knee intended to be used with the advanced pedestrian legform impactor (aPLI), a standardized

pedestrian legform impactor with an upper mass for pedestrian subsystem testing of road vehicles.

They are applicable to impact tests using the aPLI at 11,1 m/s involving:

— vehicles of category M1, except vehicles with a maximum mass above 2 500 kg and which are derived

from N1 category vehicles and where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by a maximum of 1 100 mm;

— vehicles of category N1, except where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by maximum of 1 100 mm;

— impacts to the bumper test area defined by References [1] and [2];

— pedestrian subsystem tests involving use of a legform for the purpose of evaluating compliance

with vehicle safety standards.

2 Normative references

There are no normative references in this document.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at https:// www .electropedia .org/

3.1

adult

person who is sixteen years old or older

3.2

advanced pedestrian legform impactor

aPLI

modified pedestrian legform impactor which incorporates a mass representing the inertial effect of

the upper part of a pedestrian body to enhance biofidelity and injury assessment capability (3.10) of

conventional pedestrian legforms

3.3

biofidelity

aspect of the advanced pedestrian legform impactor (aPLI) (3.2) capability to represent the impact

response of human subjects

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ISO/TS 20459:2023(E)

3.4

BLE height

bonnet leading edge height

height of the geometric trace of the upper most points of contact between a straight edge and the front-

end of the car

3.5

bumper test area

test area of the legform to bumper impact test

3.6

bumper system

component installed at the hip joint inside the upper mass composed of the bumper, the bumper mount

and the compression surface, designed to apply a force on the upper part of the femur in adduction to

enhance injury assessment capability (3.10) of the advanced pedestrian legform impactor (aPLI) (3.2)

3.7

EE method

energy-equivalent method

method of developing injury probability functions (IPFs) (3.11) for the advanced pedestrian legform

impactor (aPLI) (3.2) by transferring human injury values to those of an aPLI using the absorbed energy

3.8

high-bumper car

car with a lower bumper reference line height (3.14) of 425 mm or more

3.9

hip joint

uniaxial joint that allows abduction and adduction and connects the upper mass with the lower limb

3.10

injury assessment capability

aspect of the advanced pedestrian legform impactor (aPLI) (3.2) capability to produce peak injury values

that correlate with those obtained from human body model impact simulations

3.11

IPF

injury probability function

function which defines the relationship between a peak value of an injury metric and probability of

injury for a specific load case

3.12

ISO metric

objective rating metric used in this document to verify time histories of sensor output against

experimentally or computationally produced target time histories as detailed in ISO/TS 18571:2014

3.13

low-bumper car

car with a lower bumper reference line height (3.14) less than 425 mm

3.14

LBRL height

lower bumper reference line height

height of the geometric trace of the lowermost points of contact between a straight edge and the

bumper, measured from the ground

3.15

low-pass filter

filter which permits only low-frequency (100 Hz or less) oscillations

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ISO/TS 20459:2023(E)

3.16

paired test method

method of developing injury probability functions (IPFs) (3.11) by correlating human injury occurrence

in a specific impact configuration with the injury value measured by an ATD subjected to the same

impact as detailed in ISO/TR 12350:2013

3.17

subsystem test

test to evaluate safety performance of cars where subsystem impactors representing individual

body regions of a pedestrian are propelled into a front end of a stationary car, in impact conditions

representing specific load cases in car-pedestrian accidents

3.18

transfer function

TF

linear regression function between human injury values predicted by human body models and advanced

pedestrian legform impactor (aPLI) (3.2) injury values

3.19

TF method

transfer-function method

method of developing injury probability functions (IPFs) (3.11) for the advanced pedestrian legform

impactor (aPLI) (3.2) by converting human IPFs to those of the aPLI using corresponding transfer

functions (3.18)

4 Symbols and abbreviated terms

4.1 Symbols

See Table 1.

Table 1 — Symbols and their meanings

Symbol Meaning

C Parameter determined for the Weibull distribution for human IPFs

Scale

C

Parameter determined for the Weibull distribution for human IPFs

Shape

C

Slope of the transfer function

Slope

C

Parameter determined for the Log-Normal distribution for human IPFs

μ

C Parameter determined for the Log-Normal distribution for human IPFs

σ

C Correction factor determined to adjust to the real-world accident data

TA1

C Correction factor determined to adjust to the real-world accident data

TA2

F IPF for human

G Transfer function

I Injury metric for human

human

I Injury metric for the aPLI

aPLI

P Injury probability of human

P

Adjusted injury probability for the MCL

adj

x Value of the injury metric for the aPLI

aPLI

x Value of the injury metric for human

human

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ISO/TS 20459:2023(E)

4.2 Abbreviated terms

See Table 2.

Table 2 — Abbreviated terms and their meanings

Abbreviation Meaning

ACL Anterior Cruciate Ligament

aPLI advanced Pedestrian Legform Impactor

ATD Anthropometric Test Device

BLE Bonnet Leading Edge

BM Bending Moment

BP Bumper

EE Energy Equivalent

EEVC European Enhanced Vehicle-safety Committee

FE Finite Element

HBM Human Body Model

IPF Injury Probability Function

LBRL Lower Bumper Reference Line

MCL Medial Collateral Ligament

PCL Posterior Cruciate Ligament

PMHS Post Mortem Human Subjects

RCM Real Car Model

SCM Simplified Car Model

SP Spoiler

STP Subsystem Test Procedure

TF Transfer Function

TG Task Group

5 IPFs for the aPLI

5.1 General

The IPFs specified in this document are to be used with the aPLI for the thigh, leg and knee to predict

the probability of injuries to pedestrians when involved in real-world car-pedestrian accidents. The

IPFs provide a statistically derived relationship between the maximum values of injury metrics

obtained from a test conducted using the aPLI by following the subsystem test procedure (STP), and

the probability of injury to a corresponding body region of a pedestrian when subjected to load cases

representative of the majority of real-world accidents.

The specific load case represented by the subsystem legform test is described below:

th

— pedestrian size and weight: 175,1 cm and 76,7 kg representing a 50 percentile adult male (Reference

[3]);

— impact speed: 11,1 m/s;

— impact direction: lateral-to-medial direction to a pedestrian lower limb;

— lower-limb posture: upright (vertical to the ground) with the knee fully extended;

— impact height: sole of the foot positioned 25 mm above the ground to represent a shoe sole height.

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ISO/TS 20459:2023(E)

First, human IPFs were determined using human biomechanical data available from the literature. Data

obtained by the experiments conducted under the loading conditions equivalent to those specified in

the STP were referred to. The statistical method used to derive human IPFs follows that recommended

by ISO/TS 18506 with the covariates of pedestrian size, weight and age. The pedestrian size and weight

were determined from those specified in STP. The age was set at 60 years old that corresponds to the

average age of the subjects of the biomechanical data as this choice was found to provide the most

reasonable set of assumptions when the IPFs were fitted to the accident data. The recommended

method estimates parameters of any one of the Weibull, Log-Normal or Log-Logistic distribution

(choose the one that best fits to data) with survival analysis method. In this document, one of the three

distributions (Weibull distribution, Log-Normal distribution or Log-Logistic distribution) is used to

define human IPFs for each of the injury metrics. The formulae of the aPLI IPFs for these distributions

are presented below.

The injury probability when the Weibull distribution is applied following Formula (1):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (1)

C

Scale

where

P is the injury probability of human;

C

is the parameter determined for the Weibull distribution for human IPFs;

Scale

C

is the parameter determined for the Weibull distribution for human IPFs;

Shape

C

is the slope of the transfer function (TF);

Slope

x

is the value of the injury metric for the aPLI.

aPLI

The injury probability when the Log-Normal distribution is applied following Formula (2):

2

Cx× −− ln −tC−

()

1 1

SlopeaPLI μμ

P = exp dt (2)

∫

2

0

t

C 2ππ

2C

σσ

σσ

where

P is the injury probability of human;

C

is the parameter determined for the Log-Normal distribution for human IPFs;

μ

C

is the parameter determined for the Log-Normal distribution for human IPFs;

σ

C

is the slope of the TF;

Slope

x

is the value of the injury metric for the aPLI.

aPLI

The injury probability when the Log-Logistic distribution is applied following Formula (3):

1

P = (3)

−−1

C ×x

C

SlopeaPLI

Shape

1++

exp C

()

Scale

where

P is the injury probability of human;

C

is the parameter determined for the Log-Logistic distribution for human IPFs;

Scale

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ISO/TS 20459:2023(E)

C

is the parameter determined for the Log-Logistic distribution for human IPFs;

Shape

C

is the slope of the TF;

Slope

x

is the value of the injury metric for the aPLI.

aPLI

For each of the thigh, leg and knee, IPFs for a human body are then transferred to those of the aPLI using

a TF, which is a linear function between the maximum values of a human and aPLI injury metrics. Due

to the lack of biomechanical data, the TFs were determined from the results of computational impact

simulations using FE human body models (HBMs) and aPLI FE models in loading conditions specified

in the STP. Details of the human IPFs from which IPFs for the aPLI are derived can be found in A.2.3. For

the determination of TFs, see A.2.4 for more details.

As the IPFs converted from human IPFs using TFs are for the specific load case defined in the STP, the

number of injuries calculated from each of the injury probabilities predicted by the IPFs were compared

with that of real-world accidents. The IPFs for the knee and the leg were compensated for the real-world

observations for the injury metrics showing a significant inconsistency with accident data. Details of

the compensation to real-world accidents can be found in Annex B.

Supplemental information related to the TFs and IPFs for human is provided in Annex C and Annex D,

respectively.

5.2 Thigh

The IPF for the thigh defines probability of femur shaft fracture to a pedestrian subjected to the load

cases representative of the majority of real-world accidents as a function of maximum value of the

femur bending moment measured by the aPLI.

Figure 1 presents the IPF for the thigh. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of

the femur bending moment measured by the aPLI, and the vertical axis represents the probability of

injury.

The IPF for the thigh is given by Formula (4):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (4)

C

Scale

where

P is the injury probability for the femur shaft of human;

C

is the parameter determined for the Weibull distribution for the human IPF for the femur

Scale

shaft as described in A.2.3.4.1;

C

is the parameter determined for the Weibull distribution for the human IPF for the femur

Shape

shaft as described in A.2.3.4.1;

C

is the slope of the TF for the thigh as described in A.2.4.4.1;

Slope

x

is the femur BM measured by the aPLI in Nm.

aPLI

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 3.

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ISO/TS 20459:2023(E)

Key

X aPLI femur BM [Nm]

Y probability of femur shaft fracture

aPLI IPF for femur shaft

95 % confidence interval

observed data

Figure 1 — IPF for the femur shaft

Table 3 — Parameters of IPF for the femur shaft

C C C

Scale Shape Slope

571 11,0 1,04

5.3 Leg

The IPF for the leg defines probability of tibia shaft fracture to a pedestrian subjected to the specific

load cases representative of the majority of real-world accidents as a function of maximum value of the

tibia bending moment measured by the aPLI.

Figure 2 presents the IPF for the leg. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value

of the tibia bending moment measured by the aPLI, and the vertical axis represents the probability of

injury.

The IPF for the leg is given by the Formula (5):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (5)

C

Scale

where

P is the injury probability for the tibia shaft of human;

C

is the parameter determined for the Weibull distribution for the human IPF for the tibia

Scale

shaft as described in B.3.3;

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ISO/TS 20459:2023(E)

C

is the parameter determined for the Weibull distribution for the human IPF for the tibia

Shape

shaft as described in B.3.3;

C

is the slope of the TF for the leg as described in A.2.4.4.2;

Slope

x

is the tibia BM measured by the aPLI in Nm.

aPLI

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 4.

Key

X aPLI tibia BM [Nm]

Y probability of tibia shaft fracture

aPLI IPF for tibia shaft

95 % confidence interval

Figure 2 — IPF for the tibia shaft

Table 4 — Parameters of IPF for the tibia shaft

C C C

Scale Shape Slope

446 3,32 0,881

5.4 Knee

The IPF for the knee defines probability of complete failure of the MCL to a pedestrian subjected to the

specific load cases representative of the majority of real-world accidents as a function of maximum

value of MCL elongation measured by the aPLI.

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ISO/TS 20459:2023(E)

Figure 3 presents the IPF for the knee. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of

the MCL elongation measured by the aPLI, and the vertical axis represents the probability of injury.

The IPF for the knee is given by Formula (6):

2

Cx××C ××C −− ln −tC−

()

1 1

SlopeaPLITA1 TA2 μμ

P = exp dt (6)

∫

2

0

t

C 2ππ

2C

σσ

σσ

where

P is the injury probability for the MCL of human;

C

is the parameter determined for the Log-Normal distribution for human IPFs for the MCL

μ

as described in A.2.3.4.3;

C

is the parameter determined for the Log-Normal distribution for human IPFs for the MCL

σ

as described in A.2.3.4.3;

C

is the slope of the TF for the knee as described in A.2.4.4.3;

Slope

C

is the correction factor for lower-limb posture and impact angle determined to adjust to

TA1

the real-world accident data as described in B.3.2.2.4;

C

is the correction factor for muscle tone determined to adjust to the real-world accident

TA2

data as described in B.3.2.3;

x

is the MCL elongation measured by the aPLI in mm.

aPLI

The parameters needed to define the IPF ( C ,, C CC, and C ) for the function are described

μσ SlopeTAT12A

in Table 5.

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ISO/TS 20459:2023(E)

Key

X aPLI MCL elongation [mm]

Y probability of MCL complete rupture

aPLI IPF for MCL complete rupture

95 % confidence interval

observed data

Figure 3 — IPF for the MCL complete rupture

Table 5 — Parameters of IPF for the MCL complete rupture

C C

C C C

μμ Slope

σσ TA1 TA2

3,34 0,291 1,14 0,72 0,90

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ISO/TS 20459:2023(E)

Annex A

(informative)

Rationale regarding background and methodology to develop IPFs

for the aPLI

A.1 Historical background

A.1.1 General

Although lower extremity injuries are not life-threatening, they are frequent and potentially disabling,

resulting in a substantial cost to the victims and society. The importance of preventing this type of

injuries is illustrated by the United Nation (UN) regulations that aim to mitigate lower extremity

injuries to pedestrians hit by the front-end of cars (See References [1] and [2]).

The UN regulations initially implemented the EEVC pedestrian legform impactor that simply consists

of rigid long bones and a deformable knee joint. In order to improve injury assessment capability, a

new impactor called the Flexible Pedestrian Legform Impactor (FlexPLI) has been developed and

implemented in the phase-2 of Reference [1].

Despite a number of improvements of its capability relative to the EEVC impactor, the FlexPLI still

lacks representation of the influence of the upper part of the body. To address technical issues with

the FlexPLI, including but not limited to the lack of upper body representation, the aPLI with the upper

mass attached to the top of the conventional pedestrian legform to compensate for the lack of the upper

body has been developed. In November 2014, two ISO projects were initiated to develop Technical

Specification (TSs) for "Road vehicles - Modified pedestrian legform impactor for tests of high bumper

vehicles" and "Road vehicles - Injury criteria and risk curves for a modified pedestrian legform

impactor for use with high bumper vehicles", and the aPLI task group (TG) was established by active

participants from research institutes, dummy and instruments manufacturers, governments and car

manufacturers. The aPLI TG has conducted extensive CAE studies to identify optimized specifications

of the aPLI by utilizing HBMs, SCMs and aPLI prototype models. Based on the specifications identified, a

physical version of aPLI SBL-A was fabricated and subjected to international round robin testing.

The aPLI TG also dedicated to their effort to discuss a methodology to develop IPFs. During the

discussion, two different methods were proposed and it was difficult to choose one of the two

proposed methods because both have pros and cons. A new idea taken to facilitate the discussion was

to develop ‘virtual IPFs’ by using parametric human body models (HBMs) with the variability in the

material property of a human body incorporated. The results of this analysis along with some other

consideration resulted in a decision of applying a TF to convert IPFs for human to those for the aPLI.

Due to the lack of sufficient biomechanical data, it was necessary to determine TFs based on the

results of computer simulations using HBMs to take various load cases into consideration. Multiple

HBMs with extensive validation were used to avoid potential bias in case one single HBM is employed.

The specifications of the latest version of the aPLI hardware with the bumper system installed at the

hip joint as defined in ISO/TS 20458 were represented by FE models and used in the analyses. Real

car models (RCMs) were also used to accurately represent geometric and stiffness characteristics

of car front-end structures. The use of multiple different HBMs, RCMs and impact locations all

**...**

© ISO #### – All rights reserved

ISO/TS 20459:202#(2022(E)

ISO TC 22/SC 36/WG 6

Secretariat: XXXX

Date: 2023-02

Road vehicles - Injury risk functions for advanced Pedestrian Legform

Impactorpedestrian legform impactor (aPLI) –

TS stage

Warning for WDs and CDs

This document is not an ISO International Standard. It is being distributed for review and comment. It is subject

to change without notice and may not be referred to as an International Standard.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of

which they are aware, and to provide supporting documentation.

To help you, this guide on writing standards was produced by the ISO/TMB and is available at

A model manuscript of a draft International Standard (known as “The Rice Model”) is available at

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© ISO 202#,

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ISO/TS 20459:2023(E)

© ISO 2023, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or

utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,

or posting on the internet or an intranet, without prior written permission. Permission can be

requested from either ISO at the address below or ISO’s member body in the country of the

requester.

ISO copyright office

Ch. de Blandonnet 8 • CP 401

CH-1214 Vernier, Geneva, Switzerland

Tel. + 41 22 749 01 11

Fax + 41 22 749 09 47

copyright@iso.org

www.iso.org

www.iso.org

iv © ISO 2023 – All rights reserved

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ISO/TS 20459:2023(E)

Contents

Foreword . 6

Introduction. 7

1 Scope . 1

2 Normative references . 1

3 Terms and definitions . 1

4 Symbols and abbreviated terms . 4

4.1 Symbols . 4

4.2 Abbreviated terms . 4

5 IPFs for aPLI . 5

5.1 General . 5

5.2 Thigh . 8

5.3 Leg . 10

5.4 Knee . 13

Annex A (informative) Rationale regarding background and methodology to develop IPFs

for aPLI . 17

Annex B (informative) Adjustment of IPFs for real-world relevance . 165

Annex C (informative) Supplemental data . 218

Annex D (informative) Influence of PMHS test data (dfbetas > 0,3) against IPFs for human . 219

Bibliography . 248

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ISO/TS 20459:2023(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 the 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

patent rights. ISO shall not be held responsible for identifying any or all of such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation onof the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the World

Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT)), see

www.iso.org/iso/foreword.htmlthe following URL: .

The committee responsible for thisThis document iswas prepared by Technical Committee ISO/TC 22,

Road vehicles, Subcommittee SC 36, Safety and impact testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.

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ISO/TS 20459:2023(E)

Introduction

This ISO/TS 20459document has been prepared on the basis of the existing injury probability functions

(IPFs) to be used with an advanced Pedestrian Legform Impactorpedestrian legform impactor (aPLI)

standard build level B (SBL-B). The purpose of the TS this document is to document the IPFs for an aPLI

in a form suitable and intended for worldwide harmonized use.

In 2014, ISO/TC 22/SC 36 initiated development of the aPLI hardware and associated IPFs started, with

the aim of defining a globally accepted next-generation pedestrian legform impactor with enhanced

biofidelity and injury assessment capability, along with its IPFs, suitable for harmonized use.

Participating in the development were research institutes, dummy and instrumentation manufacturers,

governments, and car manufacturers from around the world.

IPFs for aPLI specified in this document predict injury probability to specific regions of the lower limb of

a pedestrian that correspond to maximum values of injury metrics obtained by the aPLI in a subsystem

test, as described in UN R127 References [1] and UN GTR No.9 .[2]. As the IPFs do not provide any

threshold values, users will need to determine target injury probability, based on their specific needs, to

define injury assessment reference values to be used for their test protocol.

It is also important to note that the subsystem test procedure (STP) for pedestrian protection may not be

representative of pedestrian accidents for specific injury metrics, depending on their sensitivity to

pedestrian impact conditions such as lower-limb posture and muscle tone. The IPFs for aPLI have been

validated against accident data and some ideas to compensate for the discrepancy against accident data

are presented in . Annex B.

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TECHNICAL SPECIFICATION ISO/TS 20459:2023(E)

Road vehicles - Injury risk functions for advanced Pedestrian

Legform Impactorpedestrian legform impactor (aPLI)

1 Scope

This document provides definitions, symbols and injury probability functions (IPFs) for the thigh, leg and

knee intended to be used with an advanced Pedestrian Legform Impactorpedestrian legform impactor

(aPLI), a standardized pedestrian legform impactor with an upper mass for pedestrian subsystem testing

of road vehicles. They are applicable to impact tests using an aPLI at 11,1 m/s involving:

— vehicles of category M1, except vehicles with a maximum mass above 2 500 kg and which are derived

from N1 category vehicles and where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by a maximum of 1 100 mm;

— vehicles of category N1, except where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by maximum of 1 100 mm;

— impacts to the bumper test area defined by UN R127 References [1] and UN GTR No.9 [2];

— pedestrian subsystem tests involving use of a legform for the purpose of evaluating compliance with

vehicle safety standards.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO/TS 18506, Procedure to construct injury risk curves for the evaluation of road user protection in crash

tests

There are no normative references in this document.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

adult

person who is sixteen years old or older

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ISO/TS 20459:2023(E)

3.2

advanced pedestrian legform impactor

(aPLI)

modified pedestrian legform impactor developed by ISO TC22/SC36/WG5 and WG6/aPLI Task Group,

which incorporates a mass representing the inertial effect of the upper part of a pedestrian body to

enhance biofidelity and injury assessment capability (3.10) of conventional pedestrian legforms

3.3

biofidelity

aspect of an advanced pedestrian legform impactor (aPLI) (3.2) capability to represent the impact

response of human subjects

3.4

BLE height

bonnet leading edge (BLE) height

height of the geometric trace of the upper most points of contact between a straight edge and the front-

end of a car

3.5

bumper test area

test area of the legform to bumper impact test

3.6

bumper system

component installed at the hip joint inside the upper mass composed of the bumper, the bumper mount

and the compression surface, designed to apply a force on the upper part of the femur in adduction to

enhance injury assessment capability of aPLI(3.10) of an advanced pedestrian legform impactor (aPLI)

(3.2)

3.7

EE method

energy-equivalent (EE) method

method of developing injury probability functions (IPFs) (3.11) for an advanced pedestrian legform

impactor (aPLI) (3.2) by transferring human injury values to those of an aPLI using the absorbed energy

3.8

high-bumper car

car with thea lower bumper reference line height (3.14) of 425 mm or more

3.9

hip joint

uniaxial joint that allows abduction and adduction and connects the upper mass with the lower limb

3.10

injury assessment capability

aspect of an advanced pedestrian legform impactor (aPLI) (3.2) capability to produce peak injury values

that correlate with those obtained from human body model impact simulations

3.11

IPF

injury probability function (IPF)

function which defines the relationship between a peak value of an injury metric and probability of injury

for a specific load case

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ISO/TS 20459:2023(E)

3.12

ISO metric

objective rating metric used in this Technical Specificationdocument to verify time histories of sensor

output against experimentally or computationally produced target time histories

3.13

low-bumper car

car with thea lower bumper reference line height (3.14) less than 425 mm

3.14

LBRL height

lower bumper reference line (LBRL) height

height of the geometric trace of the lower mostlowermost points of contact between a straight edge and

the bumper, measured from the ground

3.15

low-pass filter

filter which permits only low-frequency (100 Hz or less) oscillations

3.16

paired test method

method of developing injury probability functions (IPFs) (3.11) by correlating human injury occurrence

in a specific impact configuration with the injury value measured by an ATD subjected to the same impact

as detailed in ISO/TR 12350:2013

3.17

subsystem test

test to evaluate safety performance of cars where subsystem impactors representing individual body

regions of a pedestrian are propelled into a front end of a stationary car, in impact conditions

representing specific load cases in car-pedestrian accidents

3.18

transfer function

(TF)

linear regression function between human injury values predicted by human body models and advanced

pedestrian legform impactor (aPLI) (3.2) injury values

3.19

TF method

transfer-function (TF) method

method of developing injury probability functions (IPFs) (3.11) for an advanced pedestrian legform

impactor (aPLI) (3.2) by converting human IPFs to those of aPLI using corresponding transfer functions

(3.18)

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at

— IEC Electropedia: available at http://www.electropedia.org/

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ISO/TS 20459:2023(E)

84 Symbols and abbreviated terms

8.14.1 Symbols

See .Table 1.

Table 1 — Symbols and their meanings

Symbol Meaning

Split Cells

Split Cells

C 𝐶𝐶 Parameter determined for the Weibull distribution for human IPFs

Scale

Scale

C 𝐶𝐶

Shape Parameter determined for the Weibull distribution for human IPFs

Shape

C 𝐶𝐶

Slope Slope of the transfer function

Slope

C 𝐶𝐶

µ µ Parameter determined for the Log-Normal distribution for human IPFs

C 𝐶𝐶

σ Parameter determined for the Log-Normal distribution for human IPFs

σ

C 𝐶𝐶

TA1 Correction factor determined to adjust to the real-world accident data

TA1

C 𝐶𝐶

TA2 Correction factor determined to adjust to the real-world accident data

TA2

F IPF for human

G Transfer function

I 𝐼𝐼 Injury metric for human

human

human

I 𝐼𝐼 Injury metric for an aPLI

aPLI

aPLI

P Injury probability of human

P 𝑃𝑃

adj Adjusted injury probability for the MCL

adj

x 𝑥𝑥

Value of the injury metric for an aPLI

aPLI aPLI

x 𝑥𝑥

Value of the injury metric for human

human human

8.24.2 Abbreviated terms

See .Table 2.

Table 2 — Abbreviated terms and their meanings

Abbreviation Meaning and their meanings

Split Cells

Split Cells

ACL Anterior Cruciate Ligament

aPLI advanced Pedestrian Legform Impactor

ATD Anthropometric Test Device

BLE Bonnet Leading Edge

BM Bending Moment

EE Energy Equivalent

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ISO/TS 20459:2023(E)

EEVC European Enhanced Vehicle-safety Committee

FE Finite Element

HBM Human Body Model

IPF Injury Probability Function

LBRL Lower Bumper Reference Line

MCL Medial Collateral Ligament

PCL Posterior Cruciate Ligament

PMHS Post Mortem Human Subjects

RCM Real Car Model

SCM Simplified Car Model

STP Subsystem Test Procedure

TF Transfer Function

TG Task Group

95 IPFs for an aPLI

9.15.1 General

The IPFs specified in this document are to be used with the aPLI for the thigh, leg and knee to predict the

probability of injuries to pedestrians when involved in real-world car-pedestrian accidents. The IPFs

provide a statistically derived relationship between the maximum values of injury metrics obtained from

a test conducted using an aPLI by following the subsystem test procedure (STP), and the probability of

injury to a corresponding body region of a pedestrian when subjected to load cases representative of the

majority of real-world accidents.

The specific load case represented by the subsystem legform test is described below:

th

— pedestrian size and weight: 175,1 cm and 76,7 kg representing a 50 percentile adult male

(Schneider et al. ) Reference [3]);

— impact speed: 11,1 m/s;

— impact direction: lateral-to-medial direction to a pedestrian lower limb;

— lower-limb posture: upright (vertical to the ground) with the knee fully extended;

— impact height: sole of the foot positioned 25 mm above the ground to represent a shoe sole height.

First, human IPFs were determined using human biomechanical data available from the literature. Data

obtained by the experiments conducted under the loading conditions equivalent to those specified in the

STP were referred to. The statistical method used to derive human IPFs follows that recommended by

ISO/TS 18506 with the covariates of pedestrian size, weight and age. The pedestrian size and weight were

determined from those specified in STP. The age was set at 60 years old that corresponds to the average

age of the subjects of the biomechanical data as this choice was found to provide the most reasonable set

of assumptions when the IPFs were fitted to the accident data. The recommended method estimates

parameters of any one of the Weibull, Log-Normal or Log-Logistic distribution (choose the one that best

fits to data) with survival analysis method. In this document, one of the three distributions (Weibull

distribution, Log-Normal distribution or Log-Logistic distribution) is used to define human IPFs for each

of the injury metrics. The formulae of the aPLI IPFs for these distributions are presented below.

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ISO/TS 20459:2023(E)

The injury probability when the Weibull distribution is applied: following Formula (1):

C

Shape

Cx× 𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞

Slope aPLI 𝑪𝑪 ×𝒙𝒙

𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚

P=1−−exp 𝑷𝑷 =𝟏𝟏−𝐞𝐞𝐞𝐞𝐞𝐞�−� � �

𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒𝐞𝐞

C

Scale

( )

(1)

where

P is the injury probability of human;

𝐶𝐶 is the parameter determined for the Weibull distribution for human IPFs;

Scale

𝐶𝐶 is the parameter determined for the Weibull distribution for human IPFs;

Shape

𝐶𝐶 is the slope of the transfer function (TF);

Slope

𝑥𝑥 is the value of the injury metric for aPLI.

aPLI

P is the injury probability of human;

C

is the parameter determined for the Weibull distribution for human IPFs;

Scale

C is the parameter determined for the Weibull distribution for human IPFs;

Shape

C is the slope of the transfer function (TF);

Slope

x is the value of the injury metric for aPLI.

aPLI

The injury probability when the Log-Normal distribution is applied: following Formula (2):

2

𝟐𝟐

− ln −t C

C ×x ( )

11 𝑪𝑪 ×𝒙𝒙 −�𝐒𝐒𝐥𝐥𝒕𝒕−𝑪𝑪 �

Slope aPLI µ 𝟏𝟏 𝟏𝟏 𝛍𝛍

𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚

Pt= exp d 𝑷𝑷 = ∫ 𝒆𝒆𝒙𝒙𝒆𝒆� �𝒅𝒅𝒕𝒕

𝟐𝟐

𝟎𝟎

∫ 𝑪𝑪 √𝟐𝟐𝟐𝟐 𝒕𝒕 𝟐𝟐𝑪𝑪

2 𝝈𝝈 𝛔𝛔

0

t

C 2π 2C

σ σ

( )

(2)

where

P is the injury probability of human;

𝐶𝐶 is the parameter determined for the Log-Normal distribution for human IPFs;

µ

𝐶𝐶 is the parameter determined for the Log-Normal distribution for human IPFs;

σ

𝐶𝐶 is the slope of the TF;

Slope

𝑥𝑥 is the value of the injury metric for aPLI.

aPLI

P is the injury probability of human;

C is the parameter determined for the Log-Normal distribution for human IPFs;

µ

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ISO/TS 20459:2023(E)

C

is the parameter determined for the Log-Normal distribution for human IPFs;

σ

C is the slope of the TF;

Slope

x is the value of the injury metric for the aPLI.

aPLI

The injury probability when the Log-Logistic distribution is applied: following Formula (3):

1

𝟏𝟏

𝑷𝑷 =

P =

−𝟏𝟏

−1

𝑪𝑪 ×𝒙𝒙

𝑪𝑪

𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞

𝟏𝟏+� �

C ×x

C 𝐞𝐞𝐞𝐞𝐞𝐞 (𝑪𝑪 )

Slope aPLI 𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒𝐞𝐞

Shape

1 +

exp C

( )

Scale

( )

(3)

where

P is the injury probability of human;

𝐶𝐶 is the parameter determined for the Log-Logistic distribution for human IPFs;

Scale

𝐶𝐶 is the parameter determined for the Log-Logistic distribution for human IPFs;

Shape

𝐶𝐶 is the slope of the TF;

Slope

𝑥𝑥 is the value of the injury metric for aPLI.

aPLI

P is the injury probability of human;

C

is the parameter determined for the Log-Logistic distribution for human IPFs;

Scale

C is the parameter determined for the Log-Logistic distribution for human IPFs;

Shape

C is the slope of the TF;

Slope

x

is the value of the injury metric for the aPLI.

aPLI

For each of the thigh, leg and knee, IPFs for a human body are then transferred to those of the aPLI using

a TF, which is a linear function between the maximum values of a human and aPLI injury metrics. Due to

the lack of biomechanical data, the TFs were determined from the results of computational impact

simulations using FE human body models (HBMs) and aPLI FE models in loading conditions specified in

the STP. Details of the human IPFs from which IPFs for the aPLI are derived can be found in Annex . A.2.3.

For the determination of TFs, see Annex A.2.4 for more details.

As the IPFs converted from human IPFs using TFs are for the specific load case defined in the STP, the

number of injuries calculated from each of the injury probabilities predicted by the IPFs were compared

with that of real-world accidents. The IPFs for the knee and the leg were compensated for the real-world

observations for the injury metrics showing a significant inconsistency with accident data. Details of the

compensation to real-world accidents can be found in .Annex B.

Supplemental information related to the TFs and IPFs for human areis provided in Annex C and ,Annex D,

respectively.

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ISO/TS 20459:2023(E)

9.25.2 Thigh

The IPF for the thigh defines probability of femur shaft fracture to a pedestrian subjected to the load cases

representative of the majority of real-world accidents as a function of maximum value of the femur

bending moment measured by the aPLI.

Figure 1 presents the IPF for the thigh. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of the

femur bending moment measured by the aPLI, and the vertical axis represents the probability of injury.

The IPF for the thigh is given by the following formula:Formula (4):

C

Shape

Cx× 𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞

Slope aPLI 𝑪𝑪 ×𝒙𝒙

𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚

P=1−−exp 𝑷𝑷 =𝟏𝟏−𝐞𝐞𝐞𝐞𝐞𝐞�−� � �

𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒𝐞𝐞

C

Scale

( )

(4)

where

P is the injury probability for the femur shaft of human;

𝐶𝐶 is the parameter determined for the Weibull distribution for the human IPF for the femur

Scale

shaft as described in Annex ;

𝐶𝐶 is the parameter determined for the Weibull distribution for the human IPF for the femur

Shape

shaft as described in Annex ;

𝐶𝐶 is the slope of the TF for the thigh as described in Annex ;

Slope

𝑥𝑥 is the femur BM measured by aPLI in Nm.

aPLI

The parameters needed to define the IPF (𝐶𝐶 , 𝐶𝐶 and 𝐶𝐶 ) for the function are described in .

Scale Shape Slope

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ISO/TS 20459:2023(E)

1

0.9

0.8

0.7

0.6

0.5

Y

0.4

0.3

0.2

0.1

0

0 100 200 300 400 500 600 700 800

X

A C D

Key

A aPLI IPF for femur shaft

C 95% confidence interval

D Observed data

X aPLI femur BM (Nm)

Y Probability of femur shaft fracture

9.2.1.1.1.1 Figure — IPF for the femur shaft

9.2.1.1.1.2 Table — Parameters of IPF for the femur shaft

𝑪𝑪 P is the injury probability for the femur shaft of human;𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞 𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞

𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒

C is the parameter determined for the Weibull distribution for the human IPF for the femur

Scale

shaft as described in A.2.3.4.1;

C is the parameter determined for the Weibull distribution for the human IPF for the femur

Shape

shaft as described in A.2.3.4.1;

C is the slope of the TF for the thigh as described in A.2.4.4.1;

Slope

x

is the femur BM measured by the aPLI in Nm.

aPLI

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 3.

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ISO/TS 20459:2023(E)

Key

X aPLI femur BM [Nm]

Y probability of femur shaft fracture

aPLI IPF for femur shaft

95 % confidence interval

observed data

Figure 1 — IPF for the femur shaft

Table 3 — Parameters of IPF for the femur shaft

C C C

Scale Shape Slope

571 11,0 1,04

9.35.3 Leg

The IPF for the leg defines probability of tibia shaft fracture to a pedestrian subjected to the specific load

cases representative of the majority of real-world accidents as a function of maximum value of the tibia

bending moment measured by the aPLI.

Figure 2 presents the IPF for the leg. The injury probability function is shown in a solid line, with the 95 %

confidence interval shown in dotted lines. The horizontal axis represents the maximum value of the tibia

bending moment measured by the aPLI, and the vertical axis represents the probability of injury.

The IPF for the leg is given by the following formula:Formula (5):

C

Shape

Cx× 𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞

Slope aPLI 𝑪𝑪 ×𝒙𝒙

𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚

P=1−−exp 𝑷𝑷 =𝟏𝟏−𝐞𝐞𝐞𝐞𝐞𝐞�−� � �

𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒𝐞𝐞

C

Scale

( )

(5)

where

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ISO/TS 20459:2023(E)

P is the injury probability for the tibia shaft of human;

𝐶𝐶 is the parameter determined for the Weibull distribution for the human IPF for the tibia

Scale

shaft as described in Annex ;

𝐶𝐶 is the parameter determined for the Weibull distribution for the human IPF for the tibia

Shape

shaft as described in Annex ;

𝐶𝐶 is the slope of the TF for the leg as described in Annex ;

Slope

𝑥𝑥 is the tibia BM measured by aPLI in Nm.

aPLI

The parameters needed to define the IPF (𝐶𝐶 , 𝐶𝐶 and 𝐶𝐶 ) for the function are described in .

Scale Shape Slope

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ISO/TS 20459:2023(E)

1

0,9

0,8

0,7

0,6

Y 0,5

0,4

0,3

0,2

0,1

0

0 100 200 300 400 500 600 700 800

X

A C

Key

A aPLI IPF for tibia shaft

C 95% confidence interval

X aPLI tibia BM (Nm)

Y Probability of tibia shaft fracture

9.3.1.1.1.1 Figure —IPF for the tibia shaft

9.3.1.1.1.2 Table — Parameters of IPF for the tibia shaft

𝑪𝑪 P is the injury probability for the tibia shaft of human;𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐞𝐞𝐞𝐞 𝐒𝐒𝐒𝐒𝐒𝐒𝐞𝐞𝐞𝐞

𝑪𝑪

𝐒𝐒𝐒𝐒𝐚𝐚𝐒𝐒

C is the parameter determined for the Weibull distribution for the human IPF for the tibia

Scale

shaft as described in B.3.3;

C

is the parameter determined for the Weibull distribution for the human IPF for the tibia

Shape

shaft as described in B.3.3;

C is the slope of the TF for the leg as described in A.2.4.4.2;

Slope

x is the tibia BM measured by the aPLI in Nm.

aPLI

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ISO/TS 20459:2023(E)

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 4.

Key

X aPLI tibia BM [Nm]

Y probability of tibia shaft fracture

aPLI IPF for tibia shaft

95 % confidence interval

Figure 2 —IPF for the tibia shaft

Table 4 — Parameters of IPF for the tibia shaft

C C C

Scale Shape Slope

446 3,32 0,881

9.45.4 Knee

The IPF for the knee defines probability of complete failure of the MCL to a pedestrian subjected to the

specific load cases representative of the majority of real-world accidents as a function of maximum value

of MCL elongation measured by the aPLI.

Figure 3 presents the IPF for the knee. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of the

MCL elongation measured by the aPL

**...**

TECHNICAL ISO/TS

SPECIFICATION 20459

First edition

Road vehicles — Injury risk functions

for advanced pedestrian legform

impactor (aPLI)

Véhicules routiers — Critères lésionnels et courbes de risques pour

l'impacteur en forme de jambe de piéton (aPLI).

PROOF/ÉPREUVE

Reference number

ISO/TS 20459:2023(E)

© ISO 2023

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ISO/TS 20459:2023(E)

COPYRIGHT PROTECTED DOCUMENT

© ISO 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.

ISO copyright office

CP 401 • Ch. de Blandonnet 8

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Phone: +41 22 749 01 11

Email: copyright@iso.org

Website: www.iso.org

Published in Switzerland

ii

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ISO/TS 20459:2023(E)

Contents Page

Foreword .iv

Introduction .v

1 Scope . 1

2 Normative references . 1

3 Terms and definitions . 1

4 Symbols and abbreviated terms.3

4.1 Symbols . 3

4.2 Abbreviated terms . 4

5 IPFs for an aPLI .4

5.1 General . 4

5.2 Thigh . . 6

5.3 Leg. 7

5.4 Knee . . 8

Annex A (informative) Rationale regarding background and methodology to develop IPFs

for the aPLI .11

Annex B (informative) Adjustment of IPFs for real-world relevance . 103

Annex C (informative) Supplemental data . 133

Annex D (informative) Influence of PMHS test data (dfbetas > 0,3) against IPFs for human.134

Bibliography . 152

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ISO/TS 20459:2023(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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 36,

Safety and impact testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.

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ISO/TS 20459:2023(E)

Introduction

This document has been prepared on the basis of the existing injury probability functions (IPFs) to be

used with an advanced pedestrian legform impactor (aPLI) standard build level B (SBL-B). The purpose

of this document is to document the IPFs for an aPLI in a form suitable and intended for worldwide

harmonized use.

In 2014, development of the aPLI hardware and associated IPFs started, with the aim of defining

a globally accepted next-generation pedestrian legform impactor with enhanced biofidelity and

injury assessment capability, along with its IPFs, suitable for harmonized use. Participating in the

development were research institutes, dummy and instrumentation manufacturers, governments, and

car manufacturers from around the world.

IPFs for aPLI specified in this document predict injury probability to specific regions of the lower limb of

a pedestrian that correspond to maximum values of injury metrics obtained by the aPLI in a subsystem

test, as described in References [1] and [2]. As the IPFs do not provide any threshold values, users will

need to determine target injury probability, based on their specific needs, to define injury assessment

reference values to be used for their test protocol.

It is also important to note that the subsystem test procedure (STP) for pedestrian protection may not

be representative of pedestrian accidents for specific injury metrics, depending on their sensitivity to

pedestrian impact conditions such as lower-limb posture and muscle tone. The IPFs for aPLI have been

validated against accident data and some ideas to compensate for the discrepancy against accident data

are presented in Annex B.

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TECHNICAL SPECIFICATION ISO/TS 20459:2023(E)

Road vehicles — Injury risk functions for advanced

pedestrian legform impactor (aPLI)

1 Scope

This document provides definitions, symbols and injury probability functions (IPFs) for the thigh, leg

and knee intended to be used with an advanced pedestrian legform impactor (aPLI), a standardized

pedestrian legform impactor with an upper mass for pedestrian subsystem testing of road vehicles.

They are applicable to impact tests using an aPLI at 11,1 m/s involving:

— vehicles of category M1, except vehicles with a maximum mass above 2 500 kg and which are derived

from N1 category vehicles and where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by a maximum of 1 100 mm;

— vehicles of category N1, except where the driver’s position, the R-point, is either forward of the front

axle or longitudinally rearwards of the front axle transverse centreline by maximum of 1 100 mm;

— impacts to the bumper test area defined by References [1] and [2];

— pedestrian subsystem tests involving use of a legform for the purpose of evaluating compliance

with vehicle safety standards.

2 Normative references

There are no normative references in this document.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at https:// www .electropedia .org/

3.1

adult

person who is sixteen years old or older

3.2

advanced pedestrian legform impactor

aPLI

modified pedestrian legform impactor which incorporates a mass representing the inertial effect of

the upper part of a pedestrian body to enhance biofidelity and injury assessment capability (3.10) of

conventional pedestrian legforms

3.3

biofidelity

aspect of an advanced pedestrian legform impactor (aPLI) (3.2) capability to represent the impact

response of human subjects

1

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ISO/TS 20459:2023(E)

3.4

BLE height

bonnet leading edge height

height of the geometric trace of the upper most points of contact between a straight edge and the front-

end of a car

3.5

bumper test area

test area of the legform to bumper impact test

3.6

bumper system

component installed at the hip joint inside the upper mass composed of the bumper, the bumper mount

and the compression surface, designed to apply a force on the upper part of the femur in adduction to

enhance injury assessment capability (3.10) of an advanced pedestrian legform impactor (aPLI) (3.2)

3.7

EE method

energy-equivalent method

method of developing injury probability functions (IPFs) (3.11) for an advanced pedestrian legform

impactor (aPLI) (3.2) by transferring human injury values to those of an aPLI using the absorbed energy

3.8

high-bumper car

car with a lower bumper reference line height (3.14) of 425 mm or more

3.9

hip joint

uniaxial joint that allows abduction and adduction and connects the upper mass with the lower limb

3.10

injury assessment capability

aspect of an advanced pedestrian legform impactor (aPLI) (3.2) capability to produce peak injury values

that correlate with those obtained from human body model impact simulations

3.11

IPF

injury probability function

function which defines the relationship between a peak value of an injury metric and probability of

injury for a specific load case

3.12

ISO metric

objective rating metric used in this document to verify time histories of sensor output against

experimentally or computationally produced target time histories

3.13

low-bumper car

car with a lower bumper reference line height (3.14) less than 425 mm

3.14

LBRL height

lower bumper reference line height

height of the geometric trace of the lowermost points of contact between a straight edge and the

bumper, measured from the ground

3.15

low-pass filter

filter which permits only low-frequency (100 Hz or less) oscillations

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ISO/TS 20459:2023(E)

3.16

paired test method

method of developing injury probability functions (IPFs) (3.11) by correlating human injury occurrence

in a specific impact configuration with the injury value measured by an ATD subjected to the same

impact as detailed in ISO/TR 12350:2013

3.17

subsystem test

test to evaluate safety performance of cars where subsystem impactors representing individual

body regions of a pedestrian are propelled into a front end of a stationary car, in impact conditions

representing specific load cases in car-pedestrian accidents

3.18

transfer function

TF

linear regression function between human injury values predicted by human body models and advanced

pedestrian legform impactor (aPLI) (3.2) injury values

3.19

TF method

transfer-function method

method of developing injury probability functions (IPFs) (3.11) for an advanced pedestrian legform

impactor (aPLI) (3.2) by converting human IPFs to those of aPLI using corresponding transfer functions

(3.18)

4 Symbols and abbreviated terms

4.1 Symbols

See Table 1.

Table 1 — Symbols and their meanings

Symbol Meaning

C Parameter determined for the Weibull distribution for human IPFs

Scale

C

Parameter determined for the Weibull distribution for human IPFs

Shape

C

Slope of the transfer function

Slope

C

Parameter determined for the Log-Normal distribution for human IPFs

μ

C Parameter determined for the Log-Normal distribution for human IPFs

σ

C Correction factor determined to adjust to the real-world accident data

TA1

C Correction factor determined to adjust to the real-world accident data

TA2

F IPF for human

G Transfer function

I Injury metric for human

human

I Injury metric for an aPLI

aPLI

P Injury probability of human

P

Adjusted injury probability for the MCL

adj

x Value of the injury metric for an aPLI

aPLI

x Value of the injury metric for human

human

3

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ISO/TS 20459:2023(E)

4.2 Abbreviated terms

See Table 2.

Table 2 — Abbreviated terms and their meanings

Abbreviation Meaning

ACL Anterior Cruciate Ligament

aPLI advanced Pedestrian Legform Impactor

ATD Anthropometric Test Device

BLE Bonnet Leading Edge

BM Bending Moment

EE Energy Equivalent

EEVC European Enhanced Vehicle-safety Committee

FE Finite Element

HBM Human Body Model

IPF Injury Probability Function

LBRL Lower Bumper Reference Line

MCL Medial Collateral Ligament

PCL Posterior Cruciate Ligament

PMHS Post Mortem Human Subjects

RCM Real Car Model

SCM Simplified Car Model

STP Subsystem Test Procedure

TF Transfer Function

TG Task Group

5 IPFs for an aPLI

5.1 General

The IPFs specified in this document are to be used with the aPLI for the thigh, leg and knee to predict

the probability of injuries to pedestrians when involved in real-world car-pedestrian accidents. The

IPFs provide a statistically derived relationship between the maximum values of injury metrics

obtained from a test conducted using an aPLI by following the subsystem test procedure (STP), and

the probability of injury to a corresponding body region of a pedestrian when subjected to load cases

representative of the majority of real-world accidents.

The specific load case represented by the subsystem legform test is described below:

th

— pedestrian size and weight: 175,1 cm and 76,7 kg representing a 50 percentile adult male (Reference

[3]);

— impact speed: 11,1 m/s;

— impact direction: lateral-to-medial direction to a pedestrian lower limb;

— lower-limb posture: upright (vertical to the ground) with the knee fully extended;

— impact height: sole of the foot positioned 25 mm above the ground to represent a shoe sole height.

First, human IPFs were determined using human biomechanical data available from the literature. Data

obtained by the experiments conducted under the loading conditions equivalent to those specified in

the STP were referred to. The statistical method used to derive human IPFs follows that recommended

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ISO/TS 20459:2023(E)

by ISO/TS 18506 with the covariates of pedestrian size, weight and age. The pedestrian size and weight

were determined from those specified in STP. The age was set at 60 years old that corresponds to the

average age of the subjects of the biomechanical data as this choice was found to provide the most

reasonable set of assumptions when the IPFs were fitted to the accident data. The recommended

method estimates parameters of any one of the Weibull, Log-Normal or Log-Logistic distribution

(choose the one that best fits to data) with survival analysis method. In this document, one of the three

distributions (Weibull distribution, Log-Normal distribution or Log-Logistic distribution) is used to

define human IPFs for each of the injury metrics. The formulae of the aPLI IPFs for these distributions

are presented below.

The injury probability when the Weibull distribution is applied following Formula (1):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (1)

C

Scale

where

P is the injury probability of human;

C

is the parameter determined for the Weibull distribution for human IPFs;

Scale

C

is the parameter determined for the Weibull distribution for human IPFs;

Shape

C

is the slope of the transfer function (TF);

Slope

x

is the value of the injury metric for aPLI.

aPLI

The injury probability when the Log-Normal distribution is applied following Formula (2):

2

−− ln −tC−

Cx×

()

1 SlopeaPLI1 μμ

P = exp dt (2)

∫

2

0

t

C 2ππ

2C

σσ

σσ

where

P is the injury probability of human;

C

is the parameter determined for the Log-Normal distribution for human IPFs;

μ

C

is the parameter determined for the Log-Normal distribution for human IPFs;

σ

C

is the slope of the TF;

Slope

x

is the value of the injury metric for the aPLI.

aPLI

The injury probability when the Log-Logistic distribution is applied following Formula (3):

1

P = (3)

−−1

C ×x

C

SlopeaPLI

Shape

1++

exp()C

Scale

where

P is the injury probability of human;

C

is the parameter determined for the Log-Logistic distribution for human IPFs;

Scale

C

is the parameter determined for the Log-Logistic distribution for human IPFs;

Shape

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ISO/TS 20459:2023(E)

C

is the slope of the TF;

Slope

x

is the value of the injury metric for the aPLI.

aPLI

For each of the thigh, leg and knee, IPFs for a human body are then transferred to those of the aPLI using

a TF, which is a linear function between the maximum values of a human and aPLI injury metrics. Due

to the lack of biomechanical data, the TFs were determined from the results of computational impact

simulations using FE human body models (HBMs) and aPLI FE models in loading conditions specified

in the STP. Details of the human IPFs from which IPFs for the aPLI are derived can be found in A.2.3. For

the determination of TFs, see A.2.4 for more details.

As the IPFs converted from human IPFs using TFs are for the specific load case defined in the STP, the

number of injuries calculated from each of the injury probabilities predicted by the IPFs were compared

with that of real-world accidents. The IPFs for the knee and the leg were compensated for the real-world

observations for the injury metrics showing a significant inconsistency with accident data. Details of

the compensation to real-world accidents can be found in Annex B.

Supplemental information related to the TFs and IPFs for human is provided in Annex C and Annex D,

respectively.

5.2 Thigh

The IPF for the thigh defines probability of femur shaft fracture to a pedestrian subjected to the load

cases representative of the majority of real-world accidents as a function of maximum value of the

femur bending moment measured by the aPLI.

Figure 1 presents the IPF for the thigh. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of

the femur bending moment measured by the aPLI, and the vertical axis represents the probability of

injury.

The IPF for the thigh is given by Formula (4):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (4)

C

Scale

where

P is the injury probability for the femur shaft of human;

C

is the parameter determined for the Weibull distribution for the human IPF for the femur

Scale

shaft as described in A.2.3.4.1;

C

is the parameter determined for the Weibull distribution for the human IPF for the femur

Shape

shaft as described in A.2.3.4.1;

C

is the slope of the TF for the thigh as described in A.2.4.4.1;

Slope

x

is the femur BM measured by the aPLI in Nm.

aPLI

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 3.

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ISO/TS 20459:2023(E)

Key

X aPLI femur BM [Nm]

Y probability of femur shaft fracture

aPLI IPF for femur shaft

95 % confidence interval

observed data

Figure 1 — IPF for the femur shaft

Table 3 — Parameters of IPF for the femur shaft

C C C

Scale Shape Slope

571 11,0 1,04

5.3 Leg

The IPF for the leg defines probability of tibia shaft fracture to a pedestrian subjected to the specific

load cases representative of the majority of real-world accidents as a function of maximum value of the

tibia bending moment measured by the aPLI.

Figure 2 presents the IPF for the leg. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value

of the tibia bending moment measured by the aPLI, and the vertical axis represents the probability of

injury.

The IPF for the leg is given by the Formula (5):

C

Shape

Cx×

SlopeaPLI

P =−1exp − (5)

C

Scale

where

P is the injury probability for the tibia shaft of human;

C

is the parameter determined for the Weibull distribution for the human IPF for the tibia

Scale

shaft as described in B.3.3;

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ISO/TS 20459:2023(E)

C

is the parameter determined for the Weibull distribution for the human IPF for the tibia

Shape

shaft as described in B.3.3;

C

is the slope of the TF for the leg as described in A.2.4.4.2;

Slope

x

is the tibia BM measured by the aPLI in Nm.

aPLI

The parameters needed to define the IPF ( C , C and C ) for the function are described in

Scale Shape Slope

Table 4.

Key

X aPLI tibia BM [Nm]

Y probability of tibia shaft fracture

aPLI IPF for tibia shaft

95 % confidence interval

Figure 2 — IPF for the tibia shaft

Table 4 — Parameters of IPF for the tibia shaft

C C C

Scale Shape Slope

446 3,32 0,881

5.4 Knee

The IPF for the knee defines probability of complete failure of the MCL to a pedestrian subjected to the

specific load cases representative of the majority of real-world accidents as a function of maximum

value of MCL elongation measured by the aPLI.

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ISO/TS 20459:2023(E)

Figure 3 presents the IPF for the knee. The injury probability function is shown in a solid line, with the

95 % confidence interval shown in dotted lines. The horizontal axis represents the maximum value of

the MCL elongation measured by the aPLI, and the vertical axis represents the probability of injury.

The IPF for the knee is given by Formula (6):

2

Cx××C ××C −− ln −tC−

()

1 1

SlopeaPLITA1 TA2 μμ

P = exp dt (6)

∫

2

0

t

C 2ππ

2C

σσ

σσ

where

P is the injury probability for the MCL of human;

C

is the parameter determined for the Log-Normal distribution for human IPFs for the MCL

μ

as described in A.2.3.4.3;

C

is the parameter determined for the Log-Normal distribution for human IPFs for the MCL

σ

as described in A.2.3.4.3;

C

is the slope of the TF for the knee as described in A.2.4.4.3;

Slope

C

is the correction factor for lower-limb posture and impact angle determined to adjust to

TA1

the real-world accident data as described in B.3.2.2.4;

C

is the correction factor for muscle tone determined to adjust to the real-world accident

TA2

data as described in B.3.2.3;

x

is the MCL elongation measured by the aPLI in mm.

aPLI

The parameters needed to define the IPF ( C ,, C CC, and C ) for the function are described

μσ SlopeTAT12A

in Table 5.

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ISO/TS 20459:2023(E)

Key

X aPLI MCL elongation [mm]

Y probability of MCL complete rupture

aPLI IPF for MCL complete rupture

95 % confidence interval

observed data

Figure 3 — IPF for the MCL complete rupture

Table 5 — Parameters of IPF for the MCL complete rupture

C C

C C C

μμ Slope

σσ TA1 TA2

3,34 0,291 1,14 0,72 0,90

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ISO/TS 20459:2023(E)

Annex A

(informative)

Rationale regarding background and methodology to develop IPFs

for the aPLI

A.1 Historical background

A.1.1 General

Although lower extremity injuries are not life-threatening, they are frequent and potentially disabling,

resulting in a substantial cost to the victims and society. The importance of preventing this type of

injuries is illustrated by the United Nation (UN) regulations that aim to mitigate lower extremity

injuries to pedestrians hit by the front-end of cars (See References [1] and [2]).

The UN regulations initially implemented the EEVC pedestrian legform impactor that simply consists

of rigid long bones and a deformable knee joint. In order to improve injury assessment capability, a

new impactor called the Flexible Pedestrian Legform Impactor (FlexPLI) has been developed and

implemented in the phase-2 of Reference [1].

Despite a number of improvements of its capability relative to EEVC impactor, FlexPLI still lacks

representation of the influence of the upper part of the body. To address technical issues with FlexPLI,

including but not limited to the lack of upper body representation, the aPLI with the upper mass attached

to the top of the conventional pedestrian legform to compensate for the lack of the upper body has been

developed. In November 2014, two ISO projects were initiated to develop Technical Specification (TSs)

for "Road vehicles - Modified pedestrian legform impactor for tests of high bumper vehicles" and "Road

vehicles - Injury criteria and risk curves for a modified pedestrian legform impactor for use with high

bumper vehicles", and the aPLI task group (TG) was established by active participants from research

institutes, dummy and instruments manufacturers, governments and car manufacturers. The aPLI TG

has conducted extensive CAE studies to identify optimized specifications of the aPLI by utilizing HBMs,

SCMs and aPLI prototype models. Based on the specifications identified, a physical version of aPLI

SBL-A was fabricated and subjected to international round robin testing.

The aPLI TG continued the discussion of a methodology to develop IPFs, however, it was difficult to

choose one of the two proposed methods because both have pros and cons. A new idea taken to facilitate

the discussion was to develop ‘virtual IPFs’ by using parametric human body models (HBMs) with the

variability in the material property of a human body incorporated. The results of this analysis along

with some other consideration resulted in a decision of applying a TF to convert IPFs for human to those

for the aPLI.

Due to the lack of sufficient biomechanical data, it was necessary to determine TFs based on the

results of computer simulations using HBMs to take various load cases into consideration. Multiple

HBMs with extensive validation were used to avoid potential bias in case one single HBM is employed.

The specifications of the latest version of the aPLI hardware with the bumper system installed at the

hip joint as defined in ISO/TS 20458 were represented by FE models and used in the analyses. Real

car models (RCMs) were also used to accurately represent geometric and stiffness characteristics

of car front-end structures. The use of multiple different HBMs, RCMs and i

**...**

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