GB/T 39424.22020 PDF in English
GB/T 39424.22020 (GB/T39424.22020, GBT 39424.22020, GBT39424.22020)
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Road vehicles. Traffic accident analysis  Part 2: Guidelines for the use of impact severity measures
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Standards related to (historical): GB/T 39424.22020
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GB/T 39424.22020: PDF in English (GBT 39424.22020) GB/T 39424.22020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 43.020
T 04
Road vehicles  Traffic accident analysis  Part 2:
Guidelines for the use of impact severity measures
(ISO 123532:2003, MOD)
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: JUNE 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Measures of impact severity ... 5
5 Use guidelines ... 12
Annex A (Informative) Measurement methods of impact severity parameters 13
Annex B (Informative) Application examples with energy equivalent speed and
velocity change ... 22
Road vehicles  Traffic accident analysis  Part 2:
Guidelines for the use of impact severity measures
1 Scope
This Part of GB/T 39424 specifies the measures and use guidelines for the
impact severity of road vehicle accident.
This Part applies to the measurement of the impact severity of road vehicle
accident.
2 Normative references
The following documents are indispensable for the application of this document.
For the dated references, only the editions with the dates indicated are
applicable to this document. For the undated references, the latest edition
(including all the amendments) are applicable to this document.
GB/T 39424.12020 Road vehicles  Traffic accident analysis  Part 1:
Vocabulary (ISO 123531:2020, MOD)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T
39424.12020 apply.
4 Measures of impact severity
4.1 Overview
Evaluation of impact severity is divided into impact severity evaluation based
on injury outcome and impact severity evaluation based on vehicle response.
There is a corresponding relationship between the impact severity and the
injury mechanism and its outcome (doseresponse). Figure 1 shows the
subdivision phases of the corresponding relationship, i.e. three phases: pre
crash, crash and postcrash.
The complex doseresponse model of vehicle impact is divided into several
different subresponse models. There are different subresponse models in or
among the shaded areas in Figure 1. Among the parameters that affect the
 Crash pulse;
 Parameters derived from the crash pulse, and
 Dynamic and residual deformations.
Refer to A.9 for calculation of crash pulse.
In actual road vehicle accidents, residual deformation is often the only
parameter describing vehicle response. When the occupant compartment is
intruded, the residual deformation can replace the impact severity parameter,
to evaluate the occupant response.
5 Use guidelines
For different impact types, when selecting severity parameters and
measurement methods, the following principles can be followed:
 According to the input data available and the desired output data, select
appropriate measurement parameters;
 For different types of impact, select the suitable measurement parameters
(see Table 2);
 Combined use of multiple measurement parameters;
 When describing the injury outcome of different body regions in a crash,
the protective performance of the occupant compartment during intrusion
and the effect of the crash pulse shall also be considered;
 The uncertainty of different measurement parameters and the credibility of
their results shall be considered (especially when indirectlymeasured data
is involved).
used. Select the coordinate origin randomly in the undeformed or less
deformed place on the vehicle (such as the center of mounting bolt on a
bumper). Use the righthand rule to establish a threedimensional coordinate
system along the three axis directions of the vehicle. Then the coordinates of
any point can be determined.
A.1.2.2 Direct measurement
In order to accurately locate the damage surface in the damage coordinate
system, it is necessary to select enough points for measurement, which helps
to improve the accuracy of the investigation. In the measurement, the actual
damage surface is constructed by a series of nodes (except for individual small
irregular surfaces). When selecting points on the actual damage surface for
measurement, a unified selection standard needs to be used, such as a circle
with a diameter of 8 cm, which can be used as a measurement node when the
measurement site can accommodate the circle. For the irregular surface that
cannot accommodate the circle, no measurement may be required; or feature
vocabulary (such as hole) is used to describe the irregular surface.
Note: Easilydeformable coverings generally cannot be used as a representative actual
damage surface (except when the covering and the internal structure are deformed
at the same time).
In order to accurately express the crush volume, damage shape, area of indirect
crush, damage extent, and main distortion components in the three
dimensional coordinate system, it is necessary to select a sufficient number of
nodes and number them. The nodes do not need to form a unified grid form;
just record the coordinates in the threedimensional damage coordinate system.
The maximum error on the surface of the model determines the selection
criteria for the location and number of nodes of the threedimensional model.
The maximum error of the model surface is determined by the investigator, such
as ±5 cm or ±10 cm (depending on the damage). The number of measurement
nodes on the actual damage surface determines the upper and lower limits of
the model surface deviation.
The damage model can be determined by connecting adjacent measurement
nodes through a straight line. The actual damage surface refers to a series of
triangular planes determined by the connection lines of the nodes.
For each design hard point of supporting structure, the deformation tear, bend,
buckle mode of the structure, deformation location, and overall deformation
(offsetting, bowing, twisting, etc.) that affect the total energy dissipation shall be
recorded.
Each node shall be recorded in detail and clearly described, in order to verify
a) Crush volume is the volume between the undamaged vehicle exterior
surface and the exterior surface after it has been crushed by collision
forces and can be empirically related to the energy dissipated during
permanent deformation. When considering the mass of the vehicle, the
energy dissipated during the collision is related to the energy equivalent
speed (EES) and angular velocity changes. By analyzing the distribution
of crush volume on the vehicle structure, the location of the collision
impulse point can be determined.
b) The contour line of the contact zone indicates the position and orientation
of the vehicle relative to the contacting object at maximum engagement.
c) The displacement vector starts at the position before the measurement
point is damaged, and ends at the position after the point is damaged. The
weighted average of each displacement vector characterizes the direction
of the impact impulse.
d) The shape of the damage surface suggests the initial collision orientation
and relative positions of the colliding objects at maximum engagement.
e) During the collision, the indirect damage area can dissipate most of the
energy.
f) Even if the key structural parts produce the same displacement, their
different deformation modes (such as bending, wrinkling, tearing) will
absorb different energy, which will affect the estimation of the impact
impulse location and the estimation of the energy absorption of the
structural parts.
A.2 Energy equivalent speed (EES)
A.2.1 Information required for calculation
Although the energy equivalent speed (EES) is expressed in the form of speed,
it essentially represents the deformation energy; so the deformation features of
the vehicle shall be studied first.
A.2.2 Calculation method
The following methods can be used to determine the energy equivalent speed:
a) In the crash test, look for a vehicle similar to the case vehicle; compare
their deformation types; estimate the EES of the case vehicle through the
calculation formula of deformation energy;
b) On the basis of measuring the deformation value, the method of using the
Since the closing velocity is the vector difference of the impact velocity between
vehicles, the observed data for estimating the impact velocity is also applicable
to the closing velocity. For impacting a fixed object, the closing velocity of the
vehicle is equal to the impact velocity.
A.4.2 Calculation method
The calculation method is the same as that for impact velocity.
A.4.3 Output characteristics
The output result is expressed in meters per second (m/s).
A.5 Velocity change (Δv)
A.5.1 Information required for calculation
Observed data for estimating impact velocity and closing velocity can also be
used to calculate the velocity change (Δv), such as the accident scene
information described in A.3.1; including the location of the impact point, the
rest position of the vehicle, the tire mark of the ground during the collision, the
road friction coefficient, the road surface material, the travel direction of the
vehicle before the collision, etc. In the case of insufficient information at the
accident scene, the velocity change (Δv) can be calculated by the direction of
the impact force and the total energy dissipated when colliding with an object.
The direction of the impact force can be directly judged by the survey of the
colliding vehicle. The energy dissipation is estimated by the vehicle stiffness
coefficient table and measuring the crush profile.
A.5.2 Calculation method
Both forward and backward calculation methods can be used to calculate the
velocity change (Δv). For example, by analyzing the running out trajectory and
reasonably assuming the movement characteristics of the vehicle in this phase,
the separation velocity can be calculated. In the backward reconstruction, the
impact velocity can be calculated using the laws of physics; such as the law of
conservation of momentum, the law of conservation of energy, and the law of
conservation of angular momentum, etc. In the same way, parameters such as
the travel speed and the distance from the skid mark to the impact point in the
forward reconstruction can also be used to calculate the impact velocity. After
the impact velocity and separation velocity of the vehicle are determined, the
velocity change (Δv) can be obtained from the vector difference of these two
velocities. Since both the impact velocity and the separation velocity are vectors,
their directions need to be calculated in the local coordinate system. If the
velocity change (Δv) is calculated using the deformation energy of the backward
reconstruction, it is necessary to know the entire deformation energy, the
A.7 Intrusion extent
A.7.1 General
The intrusion extent refers to the residual intrusion of the intruded part of the
occupant compartment of the vehicle after an impact. Apart from the residual
intrusion in the occupant compartment, the dynamic intrusion generated during
the impact will be restored after the impact.
A.7.2 Information required for calculation
Select an area or point on the residual intrusion part of the occupant
compartment and obtain its measured value. This measured value and the
corresponding measured value of the same vehicle without deformation are
used as input data.
A.7.3 Calculation method
Compare the measured value of the residual intrusion part of the occupant
compartment with the measured value of the corresponding part on the
undeformed vehicle, to obtain the result.
A.7.4 Output characteristics
The intrusion extent can be measured in three directions; or expressed by a
resultant deformation vector (in meters); or expressed by the deformed volume
(in cubic meters) and the percentage of change in volume (or distance).
A.8 Intrusion velocity
A.8.1 Information required for calculation
It shall know the amount and time of intrusion at the time of intrusion, or the
acceleration time history of the intruding parts.
A.8.2 Calculation method
The mean intrusion velocity can be calculated by the amount of intrusion and
the elapsed time of intrusion. The time history curve of the intrusion velocity can
be obtained by integrating the acceleration curve of the intruding part, or by
analyzing the time history of the intrusion amount through highspeed film.
A.8.3 Output characteristics
The output result is expressed in meters per second (m/s).
A.9 Crash pulse
A.9.1 Description
The crash pulse can be acquired by a crash pulse recorder. If the crash pulse
at the time of the accident is recorded, a number of pulse characteristics used
to describe the impact severity can be accurately calculated. It is then possible
to analyze the link between these parameters and injury outcome.
Through calculation, the following parameters can be obtained:
 Velocity change;
 Mean acceleration;
 Duration of impact phase;
 Peak acceleration;
 Peak time.
A.9.2 Information required for calculation
The acceleration time history of the vehicle (preferably at the center of gravity)
shall be obtained as input data.
A.9.3 Calculation method
The crash pulse recorder can record the time history of linear acceleration and
rotational acceleration in one, two or three directions.
Other parameters are calculated according to parameter definitions.
A.9.4 Output characteristics
The output results include the acceleration time history during the impact phase
and the parameters calculated in A.9.1.
...... Source: Above contents are excerpted from the PDF  translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
