CEN/TR 18242:2025

SLOVENSKI STANDARD
01-februar-2026
Cestni zadrževalni sistemi - Določanje sil trka na mostovih kot posledica trka
vozila v zadrževalni sistem
Road restraint systems - Determination of collision forces on bridges as a result of an
impact of a vehicle on a restraint system
Fahrzeugrückhaltesysteme - Ermittlung der von Fahrzeugrückhaltesystemen auf
Brücken übertragenen Aufprallkräften
Ta slovenski standard je istoveten z: CEN/TR 18242:2025
ICS:
43.040.80 Sistemi za zaščito pri trku in Crash protection and
sistemi za zadrževanje restraint systems
potnikov
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 18242
TECHNICAL REPORT
RAPPORT TECHNIQUE
December 2025
TECHNISCHER REPORT
ICS 43.040.80
English Version
Road restraint systems - Determination of collision forces
on bridges as a result of an impact of a vehicle on a
restraint system Fahrzeugrückhaltesysteme - Ermittlung
der von Fahrzeugrückhaltesystemen auf Brücken
übertragenen Aufprallkräften
Fahrzeugrückhaltesysteme - Ermittlung der von
Fahrzeugrückhaltesystemen auf Brücken übertragenen
Aufprallkräften
This Technical Report was approved by CEN on 17 November 2025. It has been drawn up by the Technical Committee CEN/TC
226.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 18242:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions and abbreviations . 5
3.1 Terms and definitions . 5
3.2 Abbreviations . 5
4 Determination of load levels . 5
4.1 General . 5
4.2 Methodologies to determine collision forces on bridges . 6
4.2.1 Determination of collision forces by analytical methods . 6
4.2.2 Determination of collision forces aided by testing . 10
4.2.3 Determination of collision forces by measurement during the initial type testing . 17
Annex A (informative) Comparison of test measurements and calculation . 20
Annex B (informative) Normalised collision load . 22
Annex C (informative) Description of the typical layout of test facilities and Measurement
specifications . 23
Annex D (informative) Comparison of methods to determine characteristic loads from
measurements . 27
Bibliography . 34

European foreword
This document (CEN/TR 18242:2025) has been prepared by Technical Committee CEN/TC 226 “Road
equipment”, the secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
Introduction
According to EN 1991-2, collision forces on vehicle restraint systems (VRS) have to be taken into account
in bridge design so no damage is sustained by the bridge structure.
Over time traffic density and the weight of vehicles has increased throughout Europe, as a consequence
Road Authorities have started to require VRS with higher containment levels to protect the edge of
bridges. Due to these higher containment levels, the risk of bridge deck damage increases. It is important
for designers to account for realistic load levels.
Bridge designers apply the loads from EN 1991-2 in order to define the collision loads from a VRS, but
currently there is no guideline how to determine collision loads for VRS; just four load levels are
proposed.
Therefore, some countries already have established different national procedures and methods to classify
VRS; either by calculation, calculation aided by testing or just by testing.
The design of the anchoring system is part of the design of the VRS as stated in EN 1317-2:2010
(paragraph 4.2).
The purpose of this document is to catalogue common best practice methods and procedures to classify
VRS according to the EN 1991-2 collision force levels.
1 Scope
This document gives guidance on principles and methods to determine the forces due to the collision of
an errant vehicle with a vehicle restraint system (VRS) in bridge design and classify VRS with load.
2 Normative references
There are no normative references in this document.
3 Terms and definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
collision force on bridges
forces transferred to the bridge structure and the bridge cap due to the impact of an errant vehicle on a
VRS
3.2 Abbreviations
VRS vehicle restraint system
M moment
H applied horizontal load
M/H curve maximum’ moment of resistance’ – ‘maximum horizontal force’ curve of the
anchored steel safety barrier
4 Determination of load levels
4.1 General
When choosing a VRS, it is important that the bridge designer has accurate information pertaining to the
maximum load levels which that particular VRS will impact on the bridge deck. Methods to determine
this load level are given in specifications. The different methods given in this standard may not lead to
the same results. EN 1991-2 gives the load to be considered for accidental design situations.
The different methodologies in determining the characteristic capacity of a VRS are described in 4.2.
A typical bridge VRS may be a discontinuous face barrier, made completely or partly in metal, with
longitudinal elements supported by discrete posts anchored to the deck (discontinuous face barrier), or
continuous face barriers, generally made from concrete or from metal, with or without discrete
anchorage to the deck (continuous face barrier).
4.2 Methodologies to determine collision forces on bridges
4.2.1 Determination of collision forces by analytical methods
4.2.1.1 General
In principle analytical methods can be used for structural design according to EN 1991-2:2003, 4.7.3.3
(1) or for determination of local characteristic resistance of VRS (e.g. design of bridge cap and the
connection between cap and structure) according to EN 1991-2:2003, 4.7.3.3 (2). The methods can be
used for anchored barriers or for freestanding VRS (or a VRS with a non-structural weak anchoring for
location fixation only).
For structural design: 4.2.1.2 - 4.2.1.5
For determination of local characteristic resistance of VRS: 4.2.1.6 - 4.2.1.7
The M/H ‘maximum’ moment of resistance’ – ‘maximum horizontal force’ curve of the anchored steel
safety barrier is determined by an analytical method.
This curve corresponds to the weakest element of the configuration, which may be the post or the
anchoring in concrete.
To protect the bridge structure the results of the calculation may have additional safety factors.
4.2.1.2 M/H curve for the post
4.2.1.2.1 M/H curve of the post
The M/H curve of the post is calculated:
— according to the strong axis;
— without taking account of any instability phenomena of the post or its components.
The maximum resistance of the post is determined in accordance with the principles of the EN 1993-1-1
using the upper limit of the tensile strength of the grade of steel used, as determined in the EN 10025-2.
The curve area to be taken into account is defined by:
— M/H = 0,25 m: physically, no impact is possible at a height below 25 cm.
— M/H = real height of the post: physically, no impact is possible above the real height of the post.
4.2.1.2.2 Post with plinth at the base
In case of plinth at the base, the process is as follows:
a) The M/H curve of the post is first calculated as if there were no plinth. Each point of the curve is then
increased as follows:
1) H = H
n
where
H is the applied horizontal load
Hn is the applied horizontal load for each application height (n)
2) M = M + H*h
n plinth
where
M is the moment
M is the moment for each horizontal load applied
n
H is the applied horizontal load
hplinth is the height of the plinth
b) The M/H curve of the reinforced area just above the base plate is calculated.
4.2.1.2.3 Post with a variable cross section
In the case of a post with variable cross section, the process is as follows:
a) Determine at least 4 sections for which the M/H curves are calculated.
These are:
1) the section at the base of the profile (at the connection with the base plate);
2) the smallest section of the profile (probably above the profile);
3) the section(s) at the location of a discontinuity;
4) other section(s) at one or more pertinent locations) (= as far as possible distributed at the top of
the post.
b) The M/H is calculated for each section chosen as defined in 4.2.1.2.1, M/H curve of the post
Next, each point of each curve is raised:
1) H = H
n
where
H is the applied horizontal load
H is the applied horizontal load for each application height ( )
n n
2) M = M + H*h
n section
where
M is the moment
M is the moment for each horizontal load applied
n
H is the applied horizontal load
hsection is the height of the applied horizontal load for each section
4.2.1.3 M/H curve for the anchorage of barriers
The maximum resistance curve for anchorages calculated as follows:
2 2
   
HM
  +=  1
   
HM
 uu  
To determine M and H the characteristic value of f needs to be declared by the manufacturer.
u u u max
where
f is the upper limit for the tensile strength of the anchorage (in kN/m ) as
u max
determined in EN 10025-2
H is the applied horizontal load
H is the upper limit for the applied horizontal load
u
M is the moment
is the upper limit for the moment
Mu
4.2.1.4 M/H curve of the post and anchorage
The M/H curves for the post and the anchorage are compared and combined according to one of the
situations below. Only the pertinent area (0,25 m < M/H < real height of post) is considered.
— Situation 1: one curve is completely below the other(s). This curve determines the weak element and
therefore the maximum forces transmitted;
— Situation 2: the curves cross. In this case we can consider the weakest combination of parts of the
curves;
— Situation 3: there is only one curve available. This is considered as decisive.
4.2.1.5 M/H curve of the base plate
In the particular case where the resistance of the safety barrier is achieved by bending the base plate and
not the post, this can be taken into account in the determination of the M/H curve of the post and
anchoring posts assembly. As such systems are at present unknown, the principles (which are similar to
the determination of the M/H curves above) are not described in detail.
4.2.1.6 Determination of local characteristic resistance of discontinuous face barriers
The approach in 4.2.1.2 applies with the following deviations.
Use of yield strength rather than the upper limit of tensile strength in accordance with EN 1993-1-1.
For a realistic and sufficiently safe assessment the supporting effect of longitudinal elements (horizontal
tension band) are considered in the static system, taking into account the VRS behaviour observed during
type testing.
4.2.1.7 Determination of local characteristic resistance of continuous face barriers
The following approach applies for heavy concrete barriers. Light weight barriers (e.g. steel) or other
systems which are at present unknown, are not covered. The use of engineering methods representing
resistance behaviour of VRS (e.g. anchorages) is appropriate for the assessment of other VRS not covered.
Both, for free-standing or anchored concrete barriers the resistance is determined by friction forces
during assumed movement of the VRS.
Vertical forces resulting from VRS dead load increase due to the vehicle climbing on the traffic face of the
VRS. Consideration of the following scenario is appropriate (see Figure 1):
a) Climbing of a tandem axle with the two outer wheels onto the VRS front, axle distance 1,20 m and
wheel contact patch 40 cm x 40 cm. For the position of vertical loads it is appropriate to use a height
of 20 cm above the surface (e.g. bridge deck or cap).
b) It is appropriate to include in the distribution length of the axle load, the axle distance, the wheel
contact patch and a load distribution by 45° within the VRS.
c) EN 1991-2 contains information that is appropriate for determining the vertical axle load:
0,;75××αQ1 QK1
in case of αQ1 1,0 :,075××1,0 300 225 kN
Where
α is the load class coefficient
Q1 is the applied load
K is the total support stiffness in the longitudinal direction
The coefficient of friction concrete/concrete varies depending on the surface condition between 0,5 and
1,2. In order to cover all imponderables securely, μ = 1,2 is recommended.
= =
Key
A Joint
B Load per wheel
C Friction surface
D Load per wheel surface 40x40 cm
Friction force = µ*(g +(0,75*α *Q )/1,80)
vrs Q1 1k
Where
µ is the coefficient of friction concrete/concrete
is the dead load of v in kN/m
gvrs rs
Figure 1 — Friction of heavy concrete barriers on concrete surface
4.2.2 Determination of collision forces aided by testing
4.2.2.1 General
The identification of maximum loads acting on bridge decks during vehicle collisions with VRS is
beneficial for ensuring a safe design of the bridge structure. The most significant collision loads are the
overturning moment, the horizontal force and the vertical force; such loads have a distribution on the
length of the deck that varies rapidly during the impact. Bridge designers need the highest possible loads
to verify the structures, i.e. the values of the highest peaks of each load, averaged over predetermined
length and low-pass filtered in time with appropriate cut-off frequency.
In general, the safe design of a VRS includes load limiters that yield at the maximum impact performance
yet allowing a safe containment of the vehicle. Nevertheless, usually the maximum possible anchorage -
load does not necessarily occur during the containment test. Therefore tests are carried out on test
samples representative of the performance of the road restraint systems in terms of load transmission to
the ground. The tests are performed until the ultimate failure of the systems, and therefore the effect of
any possible vehicle is covered. Values of forces and moments in the different directions are obtained,
related to a defined point of the road restraint systems.
The ultimate strength is the maximum resistant capacity, expressed by means of forces and moments,
developed by the test sample. It is reached when the structural collapse of the sample occurs, or the
fixings or fusible elements break.
A characterization of the road restraint system is obtained in terms of the loads it transmits to the
structure, which do not depend on the containment level according to EN 1317-2:2010. This test
procedure does not substitute any of the full-scale vehicle impact tests specified by the EN 1317-
2:2010standard to determine the conformity of a road restraint system. This procedure defines
additional and complementary tests to the vehicle impact tests, which allow to obtain a measurement of
the maximum loads in order to apply them to the design or verification of the bridge deck or structure on
which the system is going to be installed.
4.2.2.2 Measurement of forces from barrier anchorages
4.2.2.2.1 General
The maximum loads transferred to the bridge deck by the anchorage can be measured by a push-pull test
on a barrier component connected to a single anchorage. The provision, by the manufacturer, of the
drawings and technical description of the road restraint system sample to be tested, including fixings and
specifications for its proper installation, gives the necessary information for the correct determination of
the test configuration by the test laboratory. A minimum requirement for the information to provide is
given in EN 1317-5:2007+A2:2012 , subclauses 5.2 and 5.4 .
It is appropriate to include in the definition of the test sample a fixing unit device (i.e. the functional unit
used to fix the system to the ground according to the design) and a post fixed to the deck.
This sample allows to characterize the behaviour of the road restraint system, including its fixing device.
The deck or structure on which the system is intended to be installed on the road is not evaluated. This
deck or structure is replaced by a support tool, which is part of the test installation. Considerations for
the provision of a test site allowing suitable installation of the test sample are given below:
a) A main base with enough mass and rigidity characteristics to develop reaction forces to the loads
transmitted during the impact test without displacements or deformations.
b) The capacity to measure forces and moments with appropriate sensors in the three coordinate axes.
Its structural and measurement capacity being sufficient to resist and obtain all the loads (Forces and
moments in the X, Y, Z axes) that are generated in the impact on the test sample.
c) Support substructure-tooling: it is the part of the test installation that is in contact with the test
sample and in which the fixing device is inserted or attached. It replaces the target deck or structure
on which the system would be installed on the road.
An adequate assembly formed by the base, the sensor and the supporting substructure is appropriate in
order to guarantee that its structural resistance is greater than the ultimate resistant force of the test
sample, and that its deformation during the test is negligible compared to that of the test sample.
A test can be considered to be valid if, during the test, any damage to the support substructure does not
prevent the ultimate strength of the test sample from being reached. In the case of an invalid test, an
appropriate course of action would be to carry out the test again using a support substructure with
enough resistance.
Document impacted by AC:2012
It is appropriate to install the test sample fixed on the test installation using the same fixing device
foreseen in the design of the system, without any modification of its material or geometry that affects its
behaviour in terms of load transmission.
In case of screwed elements, it is appropriate to take into account all the components (including washers)
provided for the joint, along with the applied torque.
The basically horizontal push or pull force F, oriented from the traffic side toward the barrier, is applied
perpendicularly to a single barrier post for discontinuous face barriers (see Figure 2 a), and to a single
element with a single anchorage for continuous face barriers (see Figure 2 b).

a) Discontinuous face barrier b) Continuous face barrier
Key
h Height of load
F Applied force
Figure 2 — Push tests on parapets anchorages
It is appropriate to apply the force at the maximum possible height, looking for the maximum overturning
moment, and at the lowest possible height, for the maximum shear force. If not defined by national
regulations, it is appropriate to consider that the top height is the mid-height of the top longitudinal
element, and that the lowest height is 0,5 m above the post base.
NOTE In Spain, two impact heights are defined, called A and B:
— Height A: is equal to the maximum height of the test sample, minus 0,2 m. This height is applicable to all
systems.
— Height B: is equal to the minimum of the following two measurements:
— 0,45 m
— for road restraint systems with longitudinal elements intended to come into contact with vehicles to carry
out their containment, the average height of the lowest of them, with a minimum value of 0,25 m.
Height B only applies to systems where the difference between height A and height B is greater than
0,30 m.
For discontinuous face barriers, additionally the measurement of longitudinal forces is required. In this
case two more tests are needed, with the push-pull force in the longitudinal direction, at the same heights
of the perpendicular tests.
Distributing the force over an adequate area avoids the occurrence of local damage to the barrier
(Figure 3).
Key
1 Load distributing pad
2 Anchorage
F Applied force
Figure 3 — Force distributed over an adequate area
When bent, posts with asymmetrical cross section (e.g. U section) or with narrow cross section (e.g. IPE
section) tend to twist significantly. In real life such twisting does not occur as long as the post is connected
to the barrier. Thus, it is appropriate to prevent it from occurring in the push-pull tests by the use of
adequate fixing devices.
During the test, it is appropriate to measure continually and to record the force using an appropriate
sampling rate.
The force can be measured by a load cell installed in different locations, as shown in the examples of
Figure 4, Force measurement. In any case, placing the load cell under the post base will result in the most
comparable measurements.
Key
1 Hammer
2 Load cell in the hammer
3 Load cell under the post base
Figure 4 — Force measurement
Recording the displacement of a point on the hammer (or of an appropriate point on the system), with a
sampling synchronised with that of the force, allows the plotting of a force-displacement diagram, should
this be required.
Adequate test data can be obtained by testing beyond the failure of the anchorage system.
Any failure, deformation or cracking of the test sample foundation during the test will invalidate the tests
results since the test is looking for the failure loads of anchorage system. A properly sized steel foundation
can be also be used.
4.2.2.2.2 Dynamic measurements
In a dynamic test, it is appropriate to ensure that the strain rate in the material that yields in the
anchorage area is close to the one in the relevant type test.
This can be done quite simply by hitting horizontally the component of the VRS with an appropriate mass,
at a speed close to the lateral component of the impact velocity of the vehicle in the initial type testing
test with a mass sufficient to produce a deflection beyond the failure of the anchorage. The mass can be
brought to the proper speed by gravity, as with a pendulum, or by other means, as with a sledgehammer
or with a rigid bogie.
It is appropriate to carry out the tests by launching an impactor device, with enough impact energy to
cause the ultimate failure of the test sample, using an impactor with a total mass of at least 1500 kg, a
width of 600 mm and height of 300 mm. The laboratory may extend the width of the impactor if
considered necessary to bring the sample to collapse.
During the tests, loading the test sample so as to reach its ultimate strength ensures that the loads
obtained are the maximum that can occur. It is desirable to verify the failure of the fixing device, the
controlled detachment of the test sample, or deformations or breakage of materials that denote the
structural exhaustion of the tested assembly.
The desirable impact speed is (35 ± 2) km/h. measured by an appropriate method, not more than 0.5m
from the impact point on the approach path.
In dynamic tests much attention must be paid to the installation of force transducers. The inertial effects
and limited resonant frequency (lowered when attaching additional masses) could cause measurements
problems with load cells, especially in highly dynamic impacts.
For a discontinuous face barrier anchorage, the hard impact of the hammer on the post produces
vibrations of the post, mostly in bending, whose frequency is too low to be filtered and whose amplitude
is so great that the measurement and the loading of the yield area can be completely altered. This hard
impact on a post does not occur in a real collision against a VRS, because of the deformation of rails, of
spacers and of the vehicle outer body.
It is desirable to reduce the amplitude of the vibrations generated by the impact of the hammer to an
acceptable level by introducing a cushion to mitigate the impact (Figure 5).
Key
1 cushion
Figure 5 — Cushion to mitigate the hard impact
Cushion type, size, thickness and stiffness/density can be chosen by the test laboratory according to post
strength (huge strength variation among different parapets)
A suitable cushion can be made of aluminium honeycomb with appropriate dimensions. For a certain
post, impact height h and impact speed, a cushion is adequate if it deforms at least 50 mm without
bottoming.
For a continuous face barrier the dynamic test cannot be done because the mass of the element is too
large. The impact of the hammer would be reacted completely by the inertia of the element with virtually
no load on the anchorage, and the element would suffer unacceptable damage.
During dynamic tests, it is appropriate to record the force and the displacement with a sampling rate of
at least 10 kHz, with the sampled data being reported using a low-pass filtered with a CFC 600, as
described in the ISO 6487, and an adequate Channel Amplitude Class (CAC) to avoid both saturation and
excessive staggering during the acquisition process.
It is desirable to acquire at least an additional 500 ms at the beginning and the end of the contact between
the impactor and the sample, in order to minimize possible unwanted effects in the filtering stage.
Accurate dynamic measurements are not easy, but performing the dynamic tests c
...