ISO/FDIS 18379-1

ISO /TC 269/SC 01/WG 9 1
Secretariat: SAC AFNOR
Date: 2026-01-29
Railway infrastructure — Ballastless track — —
Part 1:
General requirements
First edition
Date: 2025-11-27
Infrastructure ferroviaire — Voies sans ballast —
Partie 1: Exigences générales
FDIS stage
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ISO/DISFDIS 18379-1:2025 (E2026(en)
Contents
Foreword . vii
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Configuration of ballastless track . 2
4.1 General . 2
4.2 Ballastless track system, subsystems and components . 2
5 External actions . 4
5.1 Types of actions . 4
5.2 Railway traffic loading . 4
5.3 Indirect actions and conditions imposed by the substructure . 6
5.4 Environmental actions . 8
6 System requirements . 9
6.1 Track design geometry . 9
6.2 Track stability. 9
6.3 Structure gauge . 9
6.4 Design life . 9
6.5 Maintainability . 9
6.6 Environmental sustainability . 9
6.7 Noise and vibration . 10
6.8 Derailment . 10
6.9 Electrical interfaces . 10
6.10 Fixing of equipment . 11
6.11 Requirements related to the substructure. 12
6.12 Transitions . 14
6.13 Requirements related to the environment . 14
Annex A (informative) System configuration of ballastless track systems . 16
Annex B (informative) Railway traffic loading of specific regions or nations . 21
Annex C (informative) Rail temperature increase by using eddy current brake . 28
Annex D (informative) Examples of loop-free and zones with limited metal content to ensure
EMC . 32
Annex E (informative) Example of beacon mounting system . 36
Annex F (informative) Correlation between relevant regional or national standards . 37
Bibliography . 39

vi
Foreword
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This document was prepared by Technical Committee ISO/TC 269, Railway applications, Subcommittee SC 01,
Infrastructure.
A list of all parts in the ISO 18379 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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Field Code Changed
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ISO/DISFDIS 18379-1:2025 (E2026(en)
Introduction
This document is intended to be used by customers, designers and specifiers of ballastless track systems as
well as for reference and development by suppliers and construction contractors.
viii
FINAL DRAFT International Standard ISO/FDIS 18379-1:2025(en)

Railway infrastructureInfrastructure — Ballastless track —
Part 1:
General requirements
1 Scope
This document specifies the general requirements relating to the design of ballastless track systems, including
configuration of ballastless track system, subsystems and components requirements, and other related
interfaces.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
IEC 62128--1:2013, Railway applications — Fixed installations — Electrical safety, earthing and the return
circuit — Part 1: Protective provisions against electric shock
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 3.1
design life
specified period for which a ballastless track system is planned to be used for its intended purpose
3.2 3.2
electromagnetic compatibility
EMC
ability of equipment or system to function satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbances to anything in that environment
3.3 3.3
floating slab
ballastless track system where a resilient element is introduced between the load-resisting element (typically
a slab) and the substructure (3.4(3.4)) which is one kind of mass-spring system
3.4 3.4
substructure
earthworks (embankment, cutting or at-grade) or bridges (or similar civil structures) or tunnel floor which
provides support to the ballastless track system
3.5 3.5
static load
action that does not cause significant acceleration of the structure or structural members
3.6 3.6
quasi-static load
dynamic action represented by an equivalent static action in a static model
3.7 3.7
dynamic load
action that causes significant acceleration of the structure or structural members
3.8 3.8
exceptional load
infrequent load which exceeds the limit for the relevant operational conditions
3.9 3.9
filling layer
track component for fixing in position which provides connection and load transfer (full or partial) between
subsystems of a ballastless track system
3.10 3.10
pavement
layered structure that is designed to provide a durable bearing capacity
3.11 3.11
track stiffness
resistance to deformation of the entire track structure in relation to the applied force
4 Configuration of ballastless track
4.1 General
The configuration of the ballastless track is an important determinant as to how the design can be approached.
4.2 Ballastless track system, subsystems and components
A ballastless track system can consist of (but is not limited to) the following levels of subsystems and
exemplary components shown in Figure 1Figure 1.
Key
1 rail/switch and crossing
2 fastening system/fastening system for embedded rail
(e.g. clip, clamp, rail pad, adhesive/embedment material)
3 prefabricated element (e.g. sleeper, block, slab, frame)
4 intermediate layer (e.g. filling layer, boot, resilient element, fixation)
5 pavement (e.g. single-, multi-layered pavement, base layer(s))
6 intermediate layer (e.g. foil, sheeting, compensation layer)
7 substructure
1 rail/switch and crossing
2 fastening system/fastening system for embedded rail
(e.g. clip, clamp, rail pad, adhesive/embedment material)
3 prefabricated element (e.g. sleeper, block, slab, frame)
4 intermediate layer (e.g. filling layer, boot, resilient element, fixation)
5 pavement (e.g. single-, multi-layered pavement, base layer(s))
6 intermediate layer (e.g. foil, sheeting, compensation layer)
7 substructure
Figure 1 — Ballastless track system — Subsystems and components
Figure 1Figure 1 shows the structure of ballastless track system according to the subsystem and component
levels. The sequence of subsystems in vertical direction as well as the presence or absence of subsystems and
components within the ballastless track is up to the individual design. Intermediate layers may be used at
different subsystem interfaces (levels).
Examples of system configurations are given in Annex AAnnex A using the numbering system specified in
Figure 1Figure 1.
5 External actions
5.1 Types of actions
The actions on ballastless track systems are classified in the following types:
— — permanent actions, which are mainly due to the self-weight of the components of the ballastless track
system and other auxiliary elements (signals, ducts, barriers, etc) which can be eventually placed on or
attached to the layers of the system; permanent actions can be determined with the density of the
materials or the unit weight of the components;
— — variable actions, which can be due to the railway traffic (5.2(5.2),), indirect actions and conditions
imposed by the substructure (5.3(5.3),), and the environment (5.4(5.4).).
5.2 Railway traffic loading
5.2.1 General
The main function of the track is to safely guide the vehicle and to distribute the loads through the ballastless
track system to the substructure. The ballastless track system shall carry the loads from the railway traffic
over the design life within the specified operational and safety limits.
Loads are generated by:
— — static or quasi static actions;
— — dynamic actions;
— — exceptional actions.
Other loads associated with construction, maintenance and emergency access shall be considered as
necessary.
The designer shall identify all relevant load models for application, considering the proposed operating speeds
and maximum axle loads to be applied. Attention is drawn to the need to determine the worst-case
combination of vertical, lateral and longitudinal loads.
NOTE Other vehicles that run during construction, maintenance or during an emergency or at level crossings on the
track surface beside the rails are not in the scope of this document.
5.2.2 Vertical loads
5.2.2.1 Load models
Unless otherwise specified, the vertical loads shall be in accordance with relevant regional or national
standards. Relevant regional or national standards are listed in Annex FAnnex F. .
Vertical traffic load models consist of one or more loads, in a pattern which can be related to axle spacing of
rail vehicles. Different operating conditions can be defined by combinations of the loads with amplification
factors applied according to relevant rules, e.g. for design speed. Load models representing real vehicles may
be used.
5.2.2.2 Additional vertical loads
Vertical static loads act unequally on the inner and outer rails due to centrifugal effects in curves or non-
uniform load distribution. If required, such effects shall be determined on the basis of the applied vehicle
model, taking into account track alignment parameters such as cant and cant deficiency.
Additional vertical loads are specified in relevant regional or national standards, see Annex FAnnex F.
5.2.2.3 Dynamic vertical loads
Dynamic effects produced by vertical loads are dependent on factors including the running speed, the
condition of the vehicle and of the track quality. Unless otherwise specified, the dynamic loads shall be in
accordance with relevant regional or national standards. For information on vertical loads of specific regions
or nations, see Annex BAnnex B.
The dynamic effects of traffic loads can be determined from dynamic analysis of the ballastless track system
with the relevant substructure under operational train loads. Alternatively, dynamic effects can be obtained
from a quasi-static analysis with the use of the load model multiplied by a consistent dynamic amplification.
5.2.2.4 Exceptional vertical loads
The impact and frequency of exceptional loads in the design should be assessed.
5.2.3 Lateral loads
Unless otherwise specified, the lateral loads shall be in accordance with relevant regional or national
standards.
Lateral loads always act in combination with the corresponding vertical loads, see Annex BAnnex B.
The following effects shall be considered:
— — centrifugal forces (applicable to curves only);
— — nosing load to represent vehicle dynamic effects due to irregularities of vehicle running or track
irregularities;
— — gauge spreading forces (concurrent outward force in the opposite direction to the centrifugal force)
from the steering action.
5.2.4 Longitudinal loads
5.2.4.1 Braking and acceleration
Unless otherwise specified, longitudinal loads caused by braking and acceleration shall be considered in
combination with the corresponding vertical loads, and be in accordance with relevant regional or national
standards. For information on longitudinal loads of specific regions or nations, see Annex BAnnex B.
5.2.4.2 Eddy current brake (ECB)
Where applicable, effects due to ECB shall be considered. Effects of ECB systems, if used for regular service
braking are dependent on the activated brake force and the sequence of trains. Effects activated by emergency
braking are significantly higher and should be handled as exceptional loading, according to 5.2.2.45.2.2.4 and
5.2.4.35.2.4.3 for magnetic rail brakes. The effects of ECB systems in terms of operational track loading are:
— — a vertical attraction force between the brake and ferromagnetic components of the ballastless track
system and track equipment;
— — the maximum vertical attraction force activated by magnets shall be determined and specified
from the rolling stock. The attraction force can interfere with movable track components, e.g. in
switches and crossings;
— — the vertical attraction forces between the braking system and the continuous welded rail
(CWR) are usually not exceeding 40 kN/bogie and per rail due to operational and emergency braking;
— — a longitudinal rail force equal to the activated braking force;
— — heating of the rails:
— — this effect shall be calculated by increasing the maximum rail temperature. It shall also be
considered for the definition of the neutral rail temperature for making of CWR;
— — the decisive rail temperature is equivalent to overall temperature of rail cross-section not
surface temperature;
— — the use of ECB can raise temperature of the rails depending on the vertical attraction force
activated and the train sequence driven operating ECB on the same track location. An example for
additional rail constraint force calculated from rail temperature increase is given in Annex CAnnex C.
It shall also take into account the maximum contribution of ECB to operational deceleration and
sequence of trains. An example for the calculation of rail temperature increase by ECB is given in
Annex CAnnex C;;
— — alternatively, the maximum allowable rail temperature increase due to eddy current braking
shall be specified. This requires a vehicle or track based rail temperature control system for
acceptance of ECB as operational braking systems.
5.2.4.3 Exceptional longitudinal loads
Magnetic track brakes are used as emergency braking and also operational braking systems. Only thermal
effects and longitudinal loads from emergency braking should be considered as exceptional track loadings for
ballastless track systems. As long as the rail temperature increase by emergency braking does not exceed 6 K,
the case is covered by the safety margin applied for track design procedures and no further calculation is
required.
5.3 Indirect actions and conditions imposed by the substructure
5.3.1 General
This clause specifies the indirect actions and other load conditions or actions imposed by the substructure
which affect the performance of the ballastless track system.
5.3.2 Indirect actions
The effect of the following indirect actions shall be considered:
— — rheological effects (shrinkage, creep or relaxation) of concrete, cement-based materials and other
materials of the ballastless track system and the interaction of those from the substructure;
— — prestressing.
5.3.3 Earthworks
5.3.3.1 General
The characteristics and performance of an earthwork on the design of the ballastless track system shall be in
accordance with relevant regional or national standards. Relevant regional or national standards are listed in
Annex FAnnex F.
For a ballastless track system, it is necessary to limit permanent deformations (settlement or heave) as well
as elastic deformations due to variable loading. The design limits for these parameters shall be determined for
the design of the ballastless track system and to define the specification for design and construction of the
earthworks.
During construction, appropriate tests should be undertaken to ensure achievement of the designed
deformation response to load in the track formation.
5.3.3.2 Stiffness
The stiffness of the substructure shall be defined, in order to design the ballastless track system.
5.3.3.3 Bearing capacity
The limiting stress to be applied by the ballastless track system to the formation should be specified.
5.3.3.4 Residual permanent deformation
A ballastless track system does not normally tolerate significant permanent deformation of the substructure
which would adversely affect the design speed or ride quality for railway traffic. Permanent deformation
limits, e.g. due to settlement or heave, shall be specified. The effects of these indirect actions on the
performance of the ballastless track system shall be evaluated.
5.3.4 Bridges
5.3.4.1 General
The characteristics and performance of a bridge on the design of the ballastless track system shall be in
accordance with relevant regional or national standards. Relevant regional or national standards are listed in
Annex FAnnex F.
The maximum allowed deflections and rotations of the bridge deck shall be used as input conditions for the
ballastless track system design, with specific consideration of local effects at bridge deck ends.
The ballastless track design shall take into account the stresses produced due to the response of the bridge to
the applied loads and actions (i.e. concave deformed shape in the span and convex over the bridge supports).
The ballastless track design on bridges shall consider the impact of use of rail expansion devices (REDs) or
turnouts where required by the situation.
5.3.4.2 Long term bridge deformation
The relationship between the bridge deck deformation and the span or length it affects shall be considered.
Provisions for long term deformation after installation of the ballastless track shall be included in the track
system design.
Long term deformation can be caused by e.g. permanent load, seasonal temperature differences, creep and
shrinkage or relaxation of prestressed concrete elements.
The relationship between the bridge span (affected length) and the vertical bridge deck deformation shall be
calculated in accordance with the relevant regional or national standards, see Annex FAnnex F.
5.3.4.3 Bridge movements due to actions on the bridge
In accordance with relevant regional or national standards, interface limits and requirements shall be made
for actions due to railway traffic and environmental load effects on the bridge and their effect on design of the
ballastless track system.
5.3.5 Tunnels
The influence on aerodynamic effects from the ballastless track system design should be included in the
system requirements.
5.4 Environmental actions
5.4.1 General
The ballastless track system shall continue to function as intended when subjected to relevant and
representative environmental conditions. These conditions are divided into representative physical and
chemical actions. The environmental actions represent the working conditions for the ballastless track system
and shall be used for determining the performance requirements for the system. Local conditions of
temperature, humidity or other environmental actions shall be defined at the design stage.
This subclause defines the environmental actions and man-made effects acting on the ballastless track system
due to:
— — temperature;
— — earthquake.
5.4.2 Temperature
Exposure to temperature and variation in temperature shall be considered over the design life of the
ballastless track system. In the design phase, the following various aspects of exposure to temperature, where
applicable, shall be considered.
The following items shall be considered:
— — exposure to air temperature and the effect of solar radiation;
— — effects of temperature gradients during the heating and cooling cycles;
— — effects of daily and seasonal temperature changes;
— — thermal effects due to the operation of rolling stock loading, e.g. ECB (where applicable), according to
5.2.4.25.2.4.2;;
— — thermal effects during and due to installation, maintenance and operation;
— — effects of temperature exposure on the substructure and any floating slab, according to 5.35.3.
Particular attention should be paid to temperature effects contributing to horizontal and vertical movements,
interaction with the substructure and interaction with other track systems such as ballasted track and floating
slab.
5.4.3 Earthquake
The earthquake sensitivity of the substructure shall be considered, where relevant, over the design life of the
ballastless track system.
6 System requirements
6.1 Track design geometry
The ballastless track system shall provide accurate and durable geometry to the track, including the ability to
adjust the vertical and horizontal position of the rails. The design shall allow for future adjustment and
maintenance, see 6.56.5.
6.2 Track stability
The track shall provide longitudinal, lateral and vertical resistance to keep the track geometry stable and to
transfer the loads to the substructure with safety and ride comfort for the passengers. Particular attention
shall be given to track buckling resistance against longitudinal forces due to thermal actions.
6.3 Structure gauge
Design of the surface profile for the ballastless track system shall be in accordance with structure gauge
requirements in relevant regional or national standards. Relevant regional or national standards are listed in
Annex FAnnex F.
6.4 Design life
Ballastless track systems should have a design life of at least 50 years unless otherwise specified. Subsystems
and components which are subject to a shorter design life due to wear or fatigue (e.g. rails) shall include
provision for replacement.
6.5 Maintainability
The requirements for maintenance of the ballastless track system shall be considered during the design phase.
This should include inspection, repair and replacement of components, subsystems, or the entire ballastless
track system as well as most common maintenance activities, e.g. CWR stressing, rail defects, track geometry
adjustment, grinding.
6.6 Environmental sustainability
Sustainability of the ballastless track system primarily concerns various environmental parameters, for
example:
— — carbon footprint (CO2 emission, energy consumption, life-cycle analysis);
— — circular economy: re-use, recycling/ability of materials;
— — ecological impact, e.g. impact on flora and fauna;
— — other environmental impacts, including acoustics and aesthetics.
Where applicable, assessment of sustainability performance should be undertaken.
6.7 Noise and vibration
To meet noise requirements, particular track features for noise control may be incorporated in the ballastless
track system.
Vibration requirements can necessitate adjustment of properties of the track system or the introduction of
intermediate resilient elements to fulfil the performance specified or both. The track stiffness can be affected
by the requirements for groundborne noise and vibration mitigation.
6.8 Derailment
The design of the ballastless track system should consider the effects of actions due to the wheels of a derailed
vehicle. The ballastless track system shall incorporate derailment containment or protection measures where
required.
6.9 Electrical interfaces
6.9.1 General
This subclause describes generic requirements for the ballastless track system with respect to electrical and
mechanical interfaces with:
— — traction power supply systems;
— — signalling systems;
— — other track equipment.
6.9.2 Rail-to-rail electrical resistance
A rail-to-rail insulation assessment is required to ensure there is no unintentional electrical connection that
can conflict with the signalling or traction power systems. Therefore, a minimum rail-to-rail insulation shall
be provided. This requirement is expressed in terms of the resistance of fastening systems in kΩ.
NOTE See ISO 22074-5 for testing methods of the electrical resistance.
The value of resistance per unit length is obtained from laboratory tests. These measurements are taken
between both rails and multiplied by the planned support spacing (and multiplied by the number of pairs of
supports tested if more than one) or multiplied by the sample length in the case of continuously supported
(e.g. embedded) rails. The overall rail-to-rail resistance per unit length is expressed as Ω·km or kΩ·m.
6.9.3 Electrical interfaces with traction power supply systems
For electrified railways the running rails are part of the return circuit, except in special cases. The structural
and electrical properties of the ballastless track system shall be coordinated with the requirements regarding
electrical safety, earthing, bonding and the return circuit as defined in relevant regional or national standards.
Items which require attention include:
— — insulation of the rails from the structures and earth;
— — risks from arcing and other kinds of unintended electrical contact between live conductors and the
reinforcement of concrete structures;
— — provision of ducts for cables and space for the electrical connections to the rails;
— — longitudinal resistance of the running rails, which is significant for railways electrified with direct
current. It is the result of the cross-sectional area of a rail and the type of the steel.
The electrical design of the return circuit and its earthing installations is needed in order to complete the
design of the ballastless track system in accordance with an overall earthing and bonding system strategy.
This shall not apply in the case of non-earthed track systems. If a non-earthed track systems is used, the
requirements in IEC 62128-1:2013, Clause 9 shall be applied.
NOTE Additional electrical requirements arise from the needs of the signalling system, see 6.9.46.9.4, 6.9.5, 6.9.5
and 6.9.66.9.6.
6.9.4 Electrical interfaces with signalling systems
The design of the ballastless track system shall consider the constraints of the signalling system.
6.9.5 Track circuit
When the running rails are used by the signalling system, they shall have sufficient electrical conductivity.
The track circuit uses the rail-to-rail electrical insulation to detect the presence of a rail vehicle. The principle
of the detection is based on the fact that the wheelsets of the rolling stock short circuit the two rails. Minimum
rail-to-rail insulation requirements shall be in accordance with relevant regional or national standards.
6.9.6 Electromagnetic compatibility (EMC) with signalling systems
The design of the ballastless track system should consider the constraints of EMC between different
equipment, e.g. vehicle/signalling and signalling/signalling. This includes concrete construction in which
closed electrical loops of reinforcement or metal should be avoided.
Requirements for loop-free zones and requirements for zones with restricted content of metal should be
distinguished and agreed between signalling and track designers, for examples see Annex DAnnex D.
Loop-free zones can be realized by using electrical insulation between longitudinal and lateral steel
reinforcement bars or by use of non-ferrous reinforcement including fibres.
Railway signalling engineers should provide geometrical dimensions in which either loop-free reinforcement
or material with restricted content of metal is required in order to control the impact of electromagnetic
interference. These dimensions should be as small as possible to limit the structural implications.
6.10 Fixing of equipment
The design of the ballastless track system shall incorporate all equipment required (e.g. magnets, antennae,
loops, beacons, axle counters, track circuits, noise absorbing panels, level crossings, guard rails, check rails
and their connections to the track). Local changes in the track cross-section shall be accommodated in the
track design. If geometric dimensions of mounting systems for track equipment are specified, the design of the
ballastless track system shall take this into account.
NOTE A mounting system for beacons is shown in Figure E.1Figure E.1.
All loads arising from fixing of equipment shall be taken into account (e.g. beacons, earthing equipment).
Loads applied to guard rails and check rails shall be considered.
6.11 Requirements related to the substructure
6.11.1 General
This subclause specifies general requirements for the ballastless track system according to the substructure
characteristics. The required substructure characteristics are separately specified in this clause for
earthworks (cuttings, embankments or at-grade situations), bridge structures and tunnels. It also covers
transitions between these different substructure types.
6.11.2 Earthworks
The earthwork formation (cuttings, embankments or at-grade) which supports the ballastless track system
shall be able to transfer the vertical and horizontal loads including those from live loads acting on the
ballastless track system into the subsoil, without exceeding the bearing capacity or resulting in excessive
deformation. Regional or national design standards can specify particular requirements on the stiffness,
bearing capacity, permanent deformations or ground deflections for the substructure in order to ensure the
appropriate performance of the ballastless track system.
The stiffness of the substructure shall be defined at the design stage as it provides the support condition for
the ballastless track system. Appropriate testing shall be undertaken to confirm the stiffness of the
substructure in accordance with design. The minimum deformation properties of the substructure should be
taken from relevant regional or national standards, see Annex FAnnex F.
It shall be ensured that the residual amount and rate of deformation will not be larger than the limit taken into
account for the design parameters used in track structural design. Consequently, any displacement or
deformation of the substructure shall be substantially completed, and in accordance with the agreed values
before installation of ballastless track system starts.
The bearing capacity or level, for example due to settlement or heave of the substructure shall not adversely
impact the performance of the ballastless track system, the design speed and the ride quality of railway traffic.
6.11.3 Bridges
Bridges and ballastless track systems have an influence on each other. Therefore, the interaction between
them shall be taken into account in the integrated design. An integrated bridge/track design should be
executed, where appropriate. However, if the bridge and the track are designed separately, the required
characteristics of the ballastless track system shall be verified as compatible with the bridge design. If
compatibility is demonstrated, no additional checks on the bridge design are required. If compatibility is not
demonstrated, then design of the ballastless track system or the bridge design shall be adjusted to achieve
compatibility.
An integrated bridge-track design shall address, among others, the following aspects:
— — consideration of deflections and rotations of the bridge deck as input conditions for the ballastless
track system design, with specific consideration of local effects at bridge deck ends. These effects from the
bridge causing uplift, compression, lateral deformation of the rail fastenings or a combination shall be
considered;
— — definition of appropriate connection systems between the bridge girder and the track system to
achieve the desired interaction degree (e.g. monolithic, partial interaction, independent), under vertical
and horizontal actions;
— — influence of the response of the bridge to the applied loads and actions (i.e. concave deformed shape
in the span and convex over the bridge supports) on the performance of the ballastless track system;
— — anticipation of the necessity of introduction of connection devices from the construction stage of the
bridge to reduce post-installed devices which can require drilling the bridge girder;
— — impact of the use of REDs and switches and crossings on bridges where required by the situation;
— — consistent distance between the bottom of the rail and the top of the bridge girder to avoid excessive
thickness of levelling layers which maycan increase dead loads on the bridge and activate additional
creep/shrinkage effects;
— — appropriate surface finishing of the top surface of the bridge girder and compatibility of the ballastless
track components with the waterproofing layers or concrete protection layer of the bridge deck.
Specific analysis of the longitudinal interaction between the bridge and the track shall be carried out in order
to check that maximum stresses at the rail and the track components do not lead to failure or buckling. For
such an analysis, the longitudinal actions (braking/ traction, rheology and thermal effects) of both the bridge
and the track shall be considered. Appropriate longitudinal stiffness and sliding resistance of the fastening
system shall be taken into account, as well as consistent boundary conditions and eventual joints at the rails,
the track or the bridge.
The bridge design shall incorporate the interface limits and requirements for actions due to railway traffic and
environmental load effects on the bridge and their effect on the design of the ballastless track system. The
bridge design should be adapted if:
— — the angle of rotation of the adjacent bridge decks at intermediate and end supports exceeds the
relevant design limits in regional or national standards;
— — there are significant differential lateral movements between adjacent bridge decks at piers and
between bridge deck and abutment. The calculation of movements shall take into account bearing
condition and typology (e.g. pot versus spherical bearings, internal clearances/tolerances and bearing
deformation);
— — there are significant differential vertical bridge deflections at bridge joints;
— — for ballastless track systems using prefabricated elements supported by pavement, if deflection by
traffic loading exceeds the limits given by relevant regional or national standards;
— — the track construction is to take place within a time period during which concrete shrinkage and creep
maycan be significant (e.g. < 6 months).
If these requirements cannot be met by the bridge design, then the interface requirements shall be considered
jointly between bridge and track designers. It shall not be assumed that the track system designer can provide
mitigation of the exceedances (within the design) without significant cost and time implications. Any agreed
solution shall deal with the resulting actions on components to ensure a durable and efficient total system is
achieved, accounting for whole life performance.
6.11.4 Tunnels
The installation of ballastless track systems in tunnels is usually based on considerations regarding the
structural support in the base of the tunnel (e.g. modulus of elasticity of soil or structural invert), the available
cross-sectional area of the tunnel, operational safety requirements and track maintenance.
Predicted values for differential displacement between adjacent tunnel segments shall be determined as input
parameters for the design of ballastless track systems. Consideration shall be given to differential
displacement due to temperature and shrinkage effects.
6.12 Transitions
Both superstructure (track form) and substructure (earthworks, bridges and tunnels) transitions shall ensure
a gradual adaptation with respect to track geometry and track stiffness. Transition in the track form should
not coincide with transitions in the substructure.
The ballastless track system shall be designed to take account of variations in the stiffness of and between
substructures, and long-term variations of track geometry due to settlement or heave. Capability for
adjustment of the track geometry to minimize the dynamic response of the vehicles shall be provided.
The length of the transition zone depends on the design speed for the line and the differences in the settlement
and stiffness characteristics of the adjacent structure and substructure. Provisions shall therefore be made to
limit differential settlement at transitions between railway bridges, tunnels and earthworks to a level that is
compatible with the operational requirements.
6.13 Requirements related to th
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