EN 13232-3:2023

SLOVENSKI STANDARD
01-december-2023
Železniške naprave - Zgornji ustroj proge - Kretnice in križišča za Vignolove tirnice
- 3. del: Zahteve na stiku kolo-tirnica
Railway applications - Track - Switches and crossings for Vignole rails - Part 3:
Requirements for wheel/rail interaction
Bahnanwendungen - Oberbau - Weichen und Kreuzungen für Vignolschienen - Teil 3:
Anforderungen an das Zusammenspiel Rad/Schiene
Applications ferroviaires - Infrastructure - Appareils de voie - Partie 3: Exigences pour
l'interaction Roue/Rail
Ta slovenski standard je istoveten z: EN 13232-3:2023
ICS:
45.080 Tračnice in železniški deli Rails and railway
components
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13232-3
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2023
EUROPÄISCHE NORM
ICS 93.100 Supersedes EN 13232-3:2003+A1:2011
English Version
Railway applications - Track - Switches and crossings for
Vignole rails - Part 3: Requirements for wheel/rail
interaction
Applications ferroviaires - Voie - Appareils de voie Bahnanwendungen - Oberbau - Weichen und
pour rails Vignole - Partie 3 : Exigences pour Kreuzungen für Vignolschienen - Teil 3: Anforderungen
l'interaction roue/rail an das Zusammenspiel Rad/Schiene
This European Standard was approved by CEN on 23 October 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13232-3:2023 E
worldwide for CEN national Members.

Contents
European foreword .4
1 Scope .6
2 Normative references .6
3 Terms, definitions and symbols .7
4 Inputs . 11
4.1 General . 11
4.2 Wheel and track parameters . 11
4.2.1 Introduction. 11
4.2.2 Wheel profiles . 11
4.2.3 Wheelsets . 12
4.2.4 Rail and track . 12
4.2.5 Tolerances and wear . 13
4.3 Contact zone . 14
4.3.1 Introduction. 14
4.3.2 Contact danger zone . 14
4.3.3 Flangeway depth . 14
4.3.4 Flangeway width . 14
4.3.5 Flange running . 14
5 Guidance principles . 15
5.1 General . 15
5.2 Guard and check rails . 15
5.3 Wheelset guidance . 15
5.3.1 General . 15
5.3.2 Angle of attack . 16
5.3.3 Flangeway . 16
5.3.4 Gauge widening . 17
5.3.5 Check rail and common crossing nose . 17
5.3.6 Obtuse Crossings . 18
5.4 Transitional guidance . 19
5.5 Entry flares . 20
6 Rules . 20
6.1 Introduction. 20
6.2 Security against derailment . 20
6.3 Wheel profiles and wear . 21
6.4 Angle of attack Ψ . 22
6.5 Apparent wheel profiles . 23
6.6 Tangent and secant contact . 24
7 Common derailment-critical situations . 25
7.1 Tangent contact . 25
7.2 Secant contact at partially open switch tip or crossing nose . 25
7.3 Secant contact at damaged switch tip . 26
7.4 Limits. 27
8 Output - Functional and Safety Dimensions (FSDs) . 28
8.1 Introduction. 28
8.2 Switch panel . 28
8.2.1 Free wheel passage in switches F . 28
WPS
8.2.2 Entry angle θ . 29
8.2.3 Switch point relief A2 .30
8.2.4 Lateral point retraction .30
8.2.5 Lateral point machining .32
8.2.6 Track gauge in diverging track – vehicle with 3 axles .32
8.3 Common crossing panel .34
8.3.1 Fixed nose protection N .34
pcf
8.3.2 Free wheel passage in fixed common crossing F .35
wpcf
8.3.3 Free wheel passage at check rail entry F .35
wpcre
8.3.4 Free wheel passage at wing rail entry F .36
wpwre
8.3.5 Minimum flangeway depth h .38
fw
8.3.6 Flangeway width in diverging track .38
8.3.7 Parallel check rail length .40
8.3.8 Check rail and raised check rail .40
8.4 Obtuse crossing panel .41
8.4.1 Free wheel passage F .41
wpof
8.4.2 Unguided length .42
8.4.3 Check rail .44
8.4.4 Free wheel passage at check rail entry .44
8.4.5 Nose protection N .45
pof
8.5 General items (can occur in all zones within or outside S&C) .47
8.5.1 Check rail and wing rail entry flare .47
8.5.2 Flangeway width – Wheel trapping .47
9 Additional requirements .47
9.1 Introduction .47
9.2 Guidance .48
9.3 Wheel load transfer .48
9.3.1 General .48
9.3.2 Running surface design .50
9.3.3 Method of assessment .51
9.4 Insufficient wheel support or guidance .51
9.4.1 Common crossings .51
9.4.2 Obtuse crossings .51
9.4.3 Movable crossings .51
Annex A (informative) Functional and safety dimensions (FSDs). Examples used in
European Networks .52
Annex B (normative) Obtuse crossing unguided length .53
Annex C (informative) Examples of Switch Entry Angle.57
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive (EU) 2016/797 aimed to be covered .59
Bibliography .61

European foreword
This document (EN 13232-3:2023) has been prepared by Technical Committee CEN/TC 256
“Railway applications”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2024, and conflicting national standards shall
be withdrawn at the latest by April 2024.
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.
This document supersedes EN 13232-3:2003+A1:2011.
This series of standards “Railway applications – Track – Switches and crossings for Vignole rails”
covers the design and quality of switches and crossings in flat bottomed rail. The list of Parts is as
follows:
— Part 1: Definitions
— Part 2: Requirements for geometric design
— Part 3: Requirements for wheel/rail interaction
— Part 4: Actuation, locking and detection
— Part 5: Switches
— Part 6: Fixed common and obtuse crossings
— Part 7: Crossings with moveable parts
— Part 8: Expansion devices
— Part 9: Layouts
Part 1 contains terminology used throughout all parts of this series. Parts 2 to 4 contain basic design
guides and are applicable to all switch and crossing assemblies. Parts 5 to 8 deal with particular
types of equipment including their tolerances. Part 9 defines the geometric and non-geometric
acceptance criteria for layout inspection.
This document introduces more detailed requirements for wheel/rail contact geometry as well as
introducing functional and safety dimensions required for the design of switches and crossings. A
number of figures have also been updated to improve clarity.
This document has been prepared under a standardisation request addressed to [the relevant ESO]
by the European Commission. The Standing Committee of the EFTA States subsequently approves
these requests for its Member States.
For the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
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.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: 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 the United Kingdom.
1 Scope
This document defines the main wheel/track interaction criteria to be taken into account during the
geometrical design of railway switches and crossings (S&C) layouts.
It specifies:
— characterization of wheel and track dimensions;
— geometric design principles for wheel guidance;
— design principles for wheel load transfer;
— whether movable crossings are needed.
These are illustrated by their application to turnout components:
— switches;
— crossings;
— check rails,
but the principles apply equally to more complex units. There are also simplified definitions of the
safety and functional dimensions, which can be used in conjunction with the general principles as the
basis for more in-depth assessment.
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.
EN 13232-1:2023, Railway applications – Track – Switches and crossings for Vignole rails – Part 1:
Definitions
EN 13715:2020, Railway applications - Wheelsets and bogies - Wheels - Tread profile
EN 15313:2016, Railway applications - In-service wheelset operation requirements - In-service and off-
vehicle wheelset maintenance
EN 15273-1:2013+A1:2016, Railway applications - Gauges - Part 1: General - Common rules for
infrastructure and rolling stock
EN 15273-2:2013+A1:2016, Railway applications - Gauges - Part 2: Rolling stock gauge
EN 15273-3:2013+A1:2016, Railway applications - Gauges - Part 3: Structure gauges
3 Terms, definitions and symbols
For the purpose of this document the terms and definitions given in EN 13232-1:2023 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
guiding force
Y
force, acting parallel to the running surface and perpendicular to running edge, between the wheel
and the relevant track component (usually a rail)
3.2
wheel load
Q
force, acting perpendicular to the running surface, between the wheel on one hand and the relevant
track component (rail)
3.3
contact angle
γ
A
angle of the contact plane versus the track plane measured at the contact point A between the wheel
and the track component. In the case of a two-point contact, the one nearest the wheel flange shall be
considered
Note 1 to entry: see Figure 1
Key
γ contact angle
A
A contact point
Figure 1 — Contact angle
3.4
friction coefficient
μ
friction coefficient encountered at the contact point where the contact angle is determined
3.5
face of flange
q
R
parameter which characterises the flange angle of the wheel as a linear dimension. The measurement
is taken at the active side of the flange between reference points P1 and P2 as defined in Figure 2
Note 1 to entry: P1 is a reference point located at a distance 2 mm from the flange tip towards the wheel axis
Note 2 to entry: P2 is reference point on the profile, at a distance from wheel axis of 10 mm more than the
wheel radius;
Dimensions in millimetres
Key
d wheel diameter qR face of flange
D0 position of wheel tread B Width of the rim
R
Sh height of the flange P2 reference point
P1 reference point Sd flange width
A back-to-back distance S front-to-front dimesnion
R R
Figure 2 — Wheel parameters
3.6
height of the flange
S
h
height of flange measured from the tread of the wheel to the tip of the flange
Note 1 to entry: see Figure 2
3.7
back-to-back distance
A
R
distance between the back of one wheel and the back of the other wheel on the same wheelset
Note 1 to entry: see Figures 2, 5 and 31
Note 2 to entry: An index max or min is given to this symbol according respectively to the maximum and
minimum values that can occur during operation.
3.8
front-to-front dimension
S
R
distance between the from of the flange of one wheel and the front of the flange of the other wheel on
the same wheelset, measured at reference point P2
Note 1 to entry: Figures 2, 5 and 31
3.9
flange width
S
d
distance between the back of the flange and the from to the flange measure from reference point P2
Note 1 to entry: see Figures 2, 5 and 31
Note 2 to entry: An index max or min is given to this symbol according respectively to the maximum and
minimum values that can occur during operation.
3.10
switch point retraction
E
distance measured at the track gauge reference plane (part 1), between the reference line of switch
and stock rail at the actual switch toe
Note 1 to entry: see Figure 3
Key
1 Vertical stock rail
2 Inclined stock rail
E Point retraction
Z1 Depth of machining reference plane below running plane for contact surface (inside head cut) of stock
and switch rail (see EN 13232-5)
Z2 Depth of machining reference plane below running plane for running surface of switch rail (see
EN 13232-5)
Figure 3 — Switch point retraction
3.11
point retraction in fixed common crossing
reference line in a fixed common crossing which can deviate from the theoretical geometry line
Note 1 to entry: From a certain distance to the crossing point, the reference line of the Vee can, depending on
the design, be removed from this theoretical line away from the wheel flange in order to avoid contact between
both elements. This situation is described in Figure 4.

Key
1 Theoretical reference line
2 Actual reference line
3 Point retraction
4 Mathematical point (MP)
5 Actual point (RP)
Figure 4 — Point retraction in fixed common crossing
Note 2 to entry: The value of the point retraction is measured at the actual point (RP).
3.12
false flange
flange on the overhanging portion of a wheel tread caused by wear on the wheel tread in the area
where the wheel and the rail normally make contact
Note 1 to entry: see Figure 7 item 1.
4 Inputs
4.1 General
The motion of wheels and transfer of wheel loads is a complex subject, involving the accumulation of
extensive data and an understanding of dynamic effects.
By making certain assumptions it is feasible to define rules which are simple yet rigorous enough for
design of all types of switches and crossings. Some of these rules assume a 2-axle bogie or vehicle.
The need for other special requirements such as those posed by 3-axle or other vehicles shall be
stated by the customer.
4.2 Wheel and track parameters
4.2.1 Introduction
This clause deals with the key parameters needed for the analysis of the interaction between wheels
and the track, either for guidance calculations or load transfer calculations.
Wheel and track dimensions are defined below.
4.2.2 Wheel profiles
Sufficient dimensions of the cross-section or profile of a wheel are required for switch and crossing
design. As a minimum, a dimensioned profile drawing shall be provided by the customer, with the
following key dimensions as defined (see Figure 5):
— flange width, height and flange angle;
— tyre/rim width and tread angle;
— wheel diameter or radius.
Dimensions in millimetres
Key
AR back-to-back dimension BR rim width
S front-to-front dimension Z1 internal zone of flange
R
D0 position of wheel tread (1) wheel 1 (2) wheel 2 FEJ external face of rim
Sd,1,Sd,2 Flange width FIJ internal face of rim
S flange height S flange tip
h
H transition point d , d wheel diameters
2 1 2
Figure 5 — Key wheel dimensions (in addition to profile details)
4.2.3 Wheelsets
Additional parameters related to the wheelsets are required for calculations for wheelset guidance.
The Customer shall provide the following parameter values:
— wheel back-to-back
— axle spacing;
— number of axles;
— clearance of middle axles, if applicable;
— bogie spacing and minimum curve radius for vehicles.
4.2.4 Rail and track
The key parameters related to the track geometry that are used in calculations for wheelset guidance
are shown in Figure 6 and listed below:
— track radius (R);
— track gauge (G);
— dimension for nose protection (check gauge) (F);
— crossing flangeway (D).
and the following shall be provided by the Customer:
— maximum permissible check rail height above running table (H).

Key
1 Highside rail D crossing flangeway
2 Wing rail R track radius
3 Check rail F dimension for nose protection
4 Lowside rail H height of check rail
G track gauge
Figure 6 — Key track dimensions
4.2.5 Tolerances and wear
It is necessary to consider tolerances and wear in order to design correctly. These are alternatively
referred to as manufacturing tolerances and service tolerances.
If the Customer provides worn wheel profiles or amounts of wear, then these should be used.
Otherwise the assumptions made by the Supplier shall form the basis for design, and these shall be
stated. The following areas of wear shall be considered:
— back of wheel flanges;
— front of wheel flanges;
— false flanges;
— flange angle.
Locations of typical lateral wheel and track wear are shown in Figure 7. These shall be taken into
account when designing flangeway gaps. (See Clause 5).
Vertical wear, examples of which are also illustrated in Figure 7, is more relevant to wheel load
transfer. (See Clause 6).
A false flange of 2 mm shall be considered in the design.
Vertical wear to the rail head occurs but is not shown in figure.7.

Key
1 False flange 4 Wing rail wear
2 Guard or check rail wear 5 Wheel wear (front)
3 Wheel wear (back) also on left wheel 6 Vee wear
Figure 7 — Locations of wheel and rail wear
4.3 Contact zone
4.3.1 Introduction
For switch and crossing design, there are issues that shall be verified during design. These are as
follows.
4.3.2 Contact danger zone
The wheel profile supplied by the Customer shall indicate the danger zone for guidance contact,
which is that part of the wheel flange which falls on the flange radius and which therefore exceeds
the angle for safe guidance. The switch and crossing Supplier shall ensure that guidance contact does
not take place within this zone for either new or worn wheels, except where it is agreed that flange-
running is a normal operating regime.
The danger zone is illustrated in Figures 16 and 17.
4.3.3 Flangeway depth
The depth of the flangeway shall be sufficient to prevent flanges from running on the floor of the
flangeway except if otherwise required by the Customer. This shall be verified considering the
increased depth of flange of a maximum worn wheel and with the shallow flangeway of a maximum
worn running surface of a rail.
4.3.4 Flangeway width
Flangeway width is governed by a number of vehicle and track parameters as described in the
following sections.
4.3.5 Flange running
The flange running is possible in very specific cases according to customer’s requirements. The
contact point on flange occurs then naturally on the flange danger zone. The specific cases for flange
running might be perpendicular (or almost perpendicular) diamond crossings, railway and tramway
crossings or crossing used in trap turnouts. The additional assessment or simulation shall be
provided in this case to ensure safe vehicle passage.
5 Guidance principles
5.1 General
The guidance of a wheelset through switches and crossings concerns mainly the lateral or horizontal
dimensions of wheel, axle, and track. Note that, in Figures 9, 10, 11 and 12, the wheels are shown in a
simplified form as ellipses at the track gauge reference plane.
5.2 Guard and check rails
Guard and check rails are rails which bear on the face of the wheel (usually the back face) to provide
guidance (See Figure 8).
a) — Check rail
b) — Guard rail
Figure 8 — Guidance with check and guard rails
Guard rails come into operation after incipient derailment and are intended to rerail wheels once
they have begun to climb the opposite running rail. Guard rails are usually provided at specific
locations in plain track (e.g. bridges), and regarding S&C, the guard rails might be used for crossings
with movable parts as an additional rail in a similar way as the check rails are used for fixed
crossings.
Check rails are intended to make contact with the wheel back under normal conditions of operation
in order to protect the opposite running rail.
5.3 Wheelset guidance
5.3.1 General
In order to determine wheelset guidance, it is necessary to make an assumption of the way in which
the wheelset is constrained to move. The assumption is shown in Figure 9 using ellipses to represent
wheel flanges. When the wheelset, bogie or vehicle is superimposed upon the track, it moves along a
trajectory which is skewed relative to the track running edges.
Figure 9a) Unchecked Figure 9b) Checked
Key
1 Highside 5 Leading axle
2 Lowside 6 Clearance
3 Angle of attack 7 Check rail
4 Trailing axle 8 Wing rail
Figure 9 — Wheelset trajectory
Given the assumption of the mode of running and the resulting angle of attack, it is possible to
determine the adequacy of the flangeway, the effectiveness of protection to the crossing nose, and
the support for wheel load transfer.
The assumed trajectory provides for the worst case, or the maximum possible angle of attack, and
subjects the leading wheel to the closest contact with a crossing nose and subjects the trailing wheel
to the poorest load transfer.
5.3.2 Angle of attack
The greatest angle of attack is achieved when the wheelset is running around a curve. For curves
without check rails, the bogie can travel as in Figure 9a, with the high-side wheel of the leading axle
in contact with the running edge of the high-side rail and the low-side wheel of the trailing axle in
contact with the running edge of the low-side rail.
The angle of attack is usually reduced if the bogie is constrained as in Figure 9b. The leading axle
runs with the low-side inner wheel back against the check rail, and the low-side wheel of the trailing
axle is in contact with the running edge of the low-side running rail.
5.3.3 Flangeway
The flangeway shall be wide enough to allow the flanges of the wheels to pass without being trapped
or being forced to climb and derail. See Figure 10 that illustrates wheel trapping.
Key
1 Highside rail and check rail
Figure 10 — Minimum flangeway (for wheel trapping)
5.3.4 Gauge widening
Gauge widening may be applied to the lowside rail to prevent trapping of the wheels of a bogie. Refer
to Figure 11 which illustrates bogie trapping.
The extent and amount of gauge widening shall be defined by the Customer or calculated by the
Supplier based on sufficient details of the Customer's rolling stock.

Key
1 Leading axle
2 Trailing axle
3 Highside rail
4 Lowside rail
Figure 11 — Minimum track gauge (for bogie trapping)
5.3.5 Check rail and common crossing nose
A minimum parallel length of check rail shall be provided opposite the fixed crossing nose to protect
the otherwise unguided zone of the crossing, which consists of the throat flare, crossing gap and side
planing. (See Figure 12). If the parallel length is less than this minimum, it shall be agreed with the
Customer.
Key
1 Throat flare
2 Crossing gap
3 Side planing
Figure 12 — Crossing – area to be covered
5.3.6 Obtuse Crossings
A crossing gap L exists between one nose (end of the vee) of the crossing and the knuckle (smallest
gap between the wing and the check rail) as shown in Figure 13. Where obtuse crossings are used in
pairs such as in diamond crossings or slips, it is necessary to verify the extent of guidance. (See
Annex B).
Key
1 Plane of flange of leading wheel X1 Centreline to Nose – guidance re-established
2 Plane of flange of trailing wheel X2 Centreline to Knuckle where guidance is broken
3 Wheel X Unguided distance
4 Direction F Dimension for nose protection
5 Crossing gap L
6 Wheel axis
Figure 13 — Diamond crossing – Wheel trajectory
Figure 13 shows how a wheelset passes through an obtuse crossing. The value of X is the unguided
distance. In the special case of an obtuse crossing a positive value of X, which represents a partly
unguided trajectory, is permitted. However, the value of X shall, if positive, be agreed between the
Customer and the Supplier. (See also Figure 40).
5.4 Transitional guidance
Where there are both unchecked track and checked track sections together there will be zones of
transitional guidance in between. To date, however, there is no precise or widespread rule for the
choice of flare to be used to gain control of a wheel passing from unchecked to checked track.
Therefore, if the Customer has established rules and parameter values then they shall be provided to
the Supplier, or the two parties shall agree the parameter values.
5.5 Entry flares
The entry flare is the part of the check or guard rail or wing in which the flangeway gap width varies
towards the end of the check, guard rail or wing.
A low value of the entry flare, which determines a long check rail, produces perturbations for a
longer time than those observed under the same conditions for a shorter check rail with high value
for entry flare.
On the other hand, transverse forces increase with the high values of entry flare, but the energy (as
the integration of transverse force with distance) is lower for high entry flares than for lower ones.
The entry flare angle shall therefore be agreed between Customer and Supplier. (See also Annex C).
6 Rules
6.1 Introduction
The general rules are clarified as follows:
a) First, the general law for derailment calculations is described. This law is to be used for safety
calculations.
b) Secondly, a list of commonly appearing dangerous situations is given. These situations can
appear during operation and are influenced by maintenance conditions and/or design options.
c) From these considerations, functional and safety dimensions are determined later in this
standard.
6.2 Security against derailment
Security against derailment is considered to be guaranteed by limiting the ratio of guiding force Y to
actual wheel load Q. Y and Q are to be determined simultaneously. The limiting value depends on the
friction coefficient μ and contact angle γ .
A
This relation is given by Formula (1) or (2).
Y tan(γ )−µ
A
=
Q 1+µ.tan(γ )
A
(1)
or, in another form:
 
Y
γ = arctan +arctan(µ)
A
 
Q
 
(2)
From this law an admissible contact angle is given, by determining an acceptable Y/Q ratio and an
assumed friction coefficient μ. This admissible contact angle determines the contact danger zone on
the wheel, where contact with track components may not take place, to eliminate the risk of wheel
climbing.
According to experiments described in ERRI C70 RP 1, the contact angle γ shall be no smaller than
A
40°. This corresponds to a friction coefficient of 0,3 and Y/Q of 0,4.
6.3 Wheel profiles and wear
The profiles of both new and worn wheels shall be considered. Typical new and worn wheel profiles,
according to EN 13715:2020, are given in Figure 14 for information.
Owing to wear in service, the flange shape will modify significantly, especially the angle of the
outside flange face. Wheel wear is characterized by q . A minimum value of q shall be fixed, usually
R R
6,5 mm as in Figure 14.
Dimensions in millimetres
Key
R Wheel radius
Figure 14 — Typical new and worn wheel profiles
For operation on switches and crossings, sharp edges or burrs cannot be tolerated in the transition
zone between the active part of the wheel and the flange tip, (see Figure 15).
Key
1 Active part of the wheel
2 Transition zone
3 Flange tip
Figure 15 — Transition zone of the wheel
6.4 Angle of attack Ψ
The angle of attack is the sum of the following angles (see Figure 16):
— the skew Ψ , due to the clearances present in axle boxes;
— the skew Ψ , due to the clearance of the wheel axles in the track;
— the skew Ψ , i.e. the angle formed by a curved track and the parallel wheel axles of car or a
bogie;
— the geometrical angle of the switch, in switches and crossings, determined at the point where the
wheel hits the switch toe.
Key
Ψ skew due to clearances present in axle boxes
Ψ skew due to clearance of the wheel axles in the track
Ψ angle formed by a curved track and the parallel wheel axles of car or a bogie
Figure 16 — Angle of attack
6.5 Apparent wheel profiles
The contact point between rail and wheel can be determined by projection of the wheel onto a plane,
perpendicular to the running plane. The projection of the wheel on this plane is called the apparent
wheel profile.
For a wheel with its axle perpendicular to the track axis (angle = 0°), the apparent wheel profile is the
same as the cross section of the wheel. (See Figure 17). Wheel circles become straight lines by the
projection.
Key
1 Contact danger zone
Figure 17 — Wheel with angle of attack = 0°

Key
1 Contact danger zone
Figure 18 — Wheel with angle of attack ≠ 0°
Figures 17 and 18 illustrate the contact danger zone. Contact between this zone and the rail shall not
be allowed to occur. which is that part of the wheel flange which falls on the flange radius and which
therefore exceeds the angle for safe guidance. (see 6.2) The switch and crossing supplier shall ensure
that guidance contact does not take place within this zone for both new and worn wheels, except
where it is agreed that flange-running is a normal operating regime.
Owing to the angle of attack (Ψ ≠ 0°), the apparent wheel profile changes as well as the contact
position between wheel and rail (see Figure 18). The derailment risk is at its greatest when the
contact takes place in front of the wheel as friction forces lift the wheel out of the track.
6.6 Tangent and secant contact
Tangent contact appears when the wheel follows a track element (rail) with a continuous profile.
Secant contact appears when the wheel encounters an object on its route. Typical situations are:
— switch toe not protected by its stock rail;
— fixed crossing nose in case of insufficient protection by check rail;
— switch rail with damaged upper surface (tip).
7 Common derailment-critical situations
7.1 Tangent contact
The contact is similar to plain line contact. The worst case appears when a new profile with
maximum angle of attack encounters the rail. In this case the contact angle γ will be maximum. (See
A
Figure 1).
7.2 Secant contact at partially open switch tip or crossing nose
The worst case is encountered when the worn wheel hits the switch tip with a non-zero angle of
attack and when the wheel is in contact with the corresponding stock rail (see Figure 19). There are
two contact points (PC1 and PC0):

Key
1 PC1 with the switch tip at contact point 1
2 PC0 wit
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