BS EN 13848-6:2014 BSI Standards Publication Railway applications — Track — Track geometry quality Part 6: Characterisation of track geometry quality BS EN 13848-6:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 13848-6:2014 The UK participation in its preparation was entrusted to Technical Committee RAE/2, Railway Applications - Track A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2014 Published by BSI Standards Limited 2014 ISBN 978 580 77862 ICS 93.100 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2014 Amendments issued since publication Date Text affected BS EN 13848-6:2014 EN 13848-6 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM March 2014 ICS 93.100 English Version Railway applications - Track - Track geometry quality - Part 6: Characterisation of track geometry quality Applications ferroviaires - Voie - Qualité géométrique de la voie - Partie 6: Caractérisation de la qualité géométrique de la voie Bahnanwendungen - Oberbau - Qualität der Gleisgeometrie - Teil 6: Charakterisierung der geometrischen Gleislagequalität This European Standard was approved by CEN on February 2014 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 13848-6:2014 E BS EN 13848-6:2014 EN 13848-6:2014 (E) Contents Page Foreword Scope Normative references 3.1 3.2 Terms, definitions, symbols and abbreviations Terms and definitions Symbols and abbreviations 4.1 4.2 4.3 4.4 Basic principles Introduction Transparency Complexity Track-vehicle interaction 5.1 5.2 5.3 5.4 5.4.1 5.4.2 5.4.3 5.5 5.5.1 5.5.2 5.6 Assessment of track geometry quality: state-of-the-art General Standard deviation (SD) Isolated defects Combination of various parameters Combined standard deviation (CoSD) Standard deviation of the combinations of parameters Point mass acceleration method (PMA) 10 Methods based on vehicle response 10 Use of theoretical model 10 Use of direct measurement 11 Power Spectral Density (PSD) 11 Levels of aggregation and calculation methods 12 7.1 7.2 7.3 7.4 7.5 Classes of track geometry quality 12 General 12 Description of track quality classes (TQC) 13 Values of track quality classes 14 Assignment of TQCs 15 Possible application of TQCs 15 Annex A (informative) Point mass acceleration method (PMA) 17 A.1 Introduction 17 A.2 Description of the PMA model 17 A.3 Calculation of the PMA-assessment figure 17 A.4 Features of the PMA method 18 Annex B (informative) Vehicle Response Analysis methods (VRA) 19 B.1 Introduction 19 B.2 Determination of the assessment functions 19 B.3 Application of the assessment functions 21 B.4 Features of VRA methods 23 Annex C (normative) Method for calculating reference TQIs (TQIref) 24 C.1 Introduction 24 C.2 Description of the reference method 24 BS EN 13848-6:2014 EN 13848-6:2014 (E) Annex D (informative) Method of classification of alternative TQI using the TQCs 26 D.1 Introduction 26 D.2 Description of the conversion method 26 Bibliography 28 BS EN 13848-6:2014 EN 13848-6:2014 (E) Foreword This document (EN 13848-6:2014) 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 September 2014, and conflicting national standards shall be withdrawn at the latest by September 2014 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association This European Standard is one of the series EN 13848 “Railway applications – Track – Track geometry quality” as listed below: — Part 1: Characterisation of track geometry — Part 2: Measuring systems – Track recording vehicles — Part 3: Measuring systems – Track construction and maintenance machines — Part 4: Measuring systems – Manual and lightweight devices — Part 5: Geometric quality levels – Plain line — Part 6: Characterisation of track geometry quality According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom BS EN 13848-6:2014 EN 13848-6:2014 (E) Scope This European Standard characterizes the quality of track geometry based on parameters defined in EN 13848-1 and specifies the different track geometry classes which should be considered This European Standard covers the following topics: — description of track geometry quality; — classification of track quality according to track geometry parameters; — considerations on how this classification can be used; — this European Standard applies to high-speed and conventional lines of 435 mm and wider gauge; — this European Standard forms an integral part of EN 13848 series Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies EN 13848-1, Railway applications - Track - Track geometry quality - Part 1: Characterisation of track geometry Terms, definitions, symbols and abbreviations 3.1 Terms and definitions For the purposes of this document, the following terms and definitions apply 3.1.1 re-colouring algorithm which modifies the spectral content of a signal aimed to compensate or apply the characteristics of a specific measuring system Note to entry: The re-colouring is used in EN 13848 series to convert a chord measurement signal into a D1 or D2 measurement signal 3.1.2 track quality class (TQC) characterization of track geometry quality as a function of speed and expressed as a range of TQIs 3.1.3 track quality index (TQI) value that characterises track geometry quality of a track section based on parameters and measuring methods compliant with EN 13848 series 3.2 Symbols and abbreviations For the purposes of this document, the following symbols and abbreviations apply BS EN 13848-6:2014 EN 13848-6:2014 (E) Table — Symbols and abbreviations Symbol Designation Unit AL Alignment ATQI Alternative Track Quality Index CL Cross level mm CoSD Combined standard deviation mm D1 Wavelength range m < λ ≤ 25 m m D2 Wavelength range 25 m < λ ≤ 70 m m D3 Wavelength range 70 m < λ ≤ 150 m for longitudinal level Wavelength range 70 m < λ ≤ 200 m for alignment m λ Wavelength m G Track gauge mm LL Longitudinal level mm MBS Multi Body System NTQI National Track Quality Index PMA Point Mass Acceleration (method) PSD Power Spectral Density m /(1/m) SD Standard deviation mm SDLL Standard deviation longitudinal level mm SDAL Standard deviation alignment mm TQI Track Quality Index TQIref Reference Track Quality Index TQC Track Quality Class V Speed VRA Vehicle Response Analysis (method) mm km/h NOTE In this European Standard, AL stands for “alignment” and is not to be confused with AL standing for “alert limit” as defined in EN 13848–5:2008+A1:2010 Basic principles 4.1 Introduction It is necessary to standardize the way that track geometry quality is assessed in order to permit safe and costeffective railway traffic by focusing on the functional requirements of both track and vehicle Basic parameters for track geometry quality assessment As track geometry measurement, vehicles present their outputs in accordance with the parameters specified in EN 13848-1, any standardized assessment method shall be based on these parameters 4.2 Transparency Any algorithm for track geometry quality assessment complying with this standard shall be fully documented, reproducible and available in the public domain BS EN 13848-6:2014 EN 13848-6:2014 (E) 4.3 Complexity Track geometry quality should be assessed by as few TQIs as possible and the algorithm should be understandable by the user 4.4 Track-vehicle interaction Track quality assessment should reflect the principles of track-vehicle interaction For example, the track geometry defects of the same amplitude but different wavelengths lead to different vehicle responses and the required wavelength range will be different depending on the track-vehicle interaction parameters to be assessed Assessment of track geometry quality: state-of-the-art 5.1 General Track geometry quality can be characterized by various TQIs according to the level of aggregation they are used for The TQIs described in the following sub-clauses are used by at least one of the European Railway Networks They represent the current state-of-the-art of description of track geometry quality 5.2 Standard deviation (SD) The standard deviation is one of the most commonly used TQIs by European Railway Networks It represents the dispersion of a signal over a given track section, in relation to the mean value of this signal over the considered section N SD = ∑ (x i =1 i − x) N −1 where N is the number of values in the sample; xi is the current value of a signal; x is the mean value of a signal; SD NOTE is the standard deviation Standard deviation is linked to the energy of the signal in a given wavelength range [λ1, λ2] according to the following relationship: λ2 SD = ∫ S xx (ν )dν λ1 , where Sxx is the PSD described in 5.6 below SD is commonly calculated for the following parameters: — Longitudinal level D1; — Alignment D1 It is also calculated for other parameters such as: — Twist; — Track gauge; — Cross level; BS EN 13848-6:2014 EN 13848-6:2014 (E) — Longitudinal level D2; — Alignment D2 For longitudinal level and alignment it is recommended to calculate SD separately for each rail It may also be calculated differently (for example: mean of both rails, worst or best of either rail or outer rail in curves) Length of track section used for standard deviation has influence on the result If comparable results are expected, only one length should be used Commonly, for maintenance reasons standard deviation is calculated over a length of 200 m It may be calculated either at fixed distances without overlap or with overlap, as a sliding standard deviation Calculation of standard deviation is also done over longer distances such as km, an entire line or an entire network NOTE made Distinction between specific track sections, such as plain lines, stations and switches and crossings, can also be When calculating SD for twist, track gauge and cross level attention should be paid on the possible influence of the quasi-static part of the signals 5.3 Isolated defects Isolated defects may present a derailment risk; however counting the number of isolated defects exceeding a specified threshold such as intervention limit and alert limit on a given fixed length of track can be representative of the track geometry quality This method is used by several European Railway Networks The number of isolated defects per unit of track length is commonly counted for the following parameters: — Longitudinal level D1; — Alignment D1; — Twist; — Track gauge; — Cross level It can be also counted for the following parameters: — Longitudinal level D2; — Alignment D2 Commonly, the number of isolated defects is counted over km or more It may also be counted over 100 m or 200 m of track If required, distinction between specific track sections can be made, such as plain lines, stations and switches and crossings Alternatively a calculation can be made to specify what percentage of a line exceeds a certain threshold level 5.4 Combination of various parameters 5.4.1 Combined standard deviation (CoSD) Assessment of the overall track geometry quality of a track section (200 m, 000 m ) can be done by a combination of weighted standard deviations of individual geometric parameters An example of such a TQI is given below BS EN 13848-6:2014 EN 13848-6:2014 (E) — monitoring of the global quality of the track for contractual purposes, for example between infrastructure manager and the infrastructure owner; — contractual purposes between train operator and infrastructure owner; — design of a vehicle according to ride quality requirements and track quality of the lines where the vehicle will run; — selection of track sections for vehicle acceptance For every possible use of the TQCs the recommended methods are given in the table below where the symbols “++ / + / _ / _ _” range from the most relevant to the least relevant method Table — Relevance of assignment method for the application of TQC 16 Application Maximum value Mean value Percentile of a distribution of TQIsref Percentage of a required TQC Key performance indicator used in a high level maintenance strategy + ++ ++ Detailed working plan for track maintenance ++ ++ + + Acceptance of track works influencing the track geometry quality ++ + + Monitoring of the global quality of the track for contractual purposes between infrastructure manager and the infrastructure owner _ ++ ++ Contractual purposes between train operator and infrastructure owner + + ++ Design of a vehicle according to ride quality requirements and track quality of the lines where the vehicle will run + + ++ + Selection of track sections for vehicle acceptance + + ++ + BS EN 13848-6:2014 EN 13848-6:2014 (E) Annex A (informative) Point mass acceleration method (PMA) A.1 Introduction This annex gives more details about the background and the recommended application of the PMA method described in 5.4.3 A.2 Description of the PMA model The PMA method is based on a simple model as follows: — The PMA model considers an unsprung virtual vehicle It is assumed to be a point mass, thus only the motion of the centre of gravity is investigated This point mass is guided in a certain distance (z) over the centreline of the actual track gauge — The point mass is moved at a constant speed corresponding to the maximum line speed over a measured track section — The geometrical imperfection of a measured track can be described by the longitudinal level and alignment of both rails — Due to the geometrical imperfection of the track, which is described by the longitudinal level and alignment of both rails, the point mass incurs accelerations ay and az in the horizontal and vertical directions — The vectorial summation of these accelerations is used to characterize the track quality A.3 Calculation of the PMA-assessment figure Setting up the equations of motion and neglecting mathematical terms of higher order lead to the formula for the acceleration: ay = c ⋅ ν n ( AL"− Ψ.LL"+ z ⋅ ( LL' ' '− Ψ" )) a z = c ⋅ v n ( LL"+ Ψ ⋅ AL"+ z ⋅ ( Ψ '² + LL"²)) Vectorial summation of both acceleration components lead to the final assessment figure: ayz = ay + az where v maximum line speed; LL longitudinal level D1, average of left and right rails; AL alignment D1, average of left and right rails; Ψ (LL left rail – LL right rail)/d; 17 BS EN 13848-6:2014 EN 13848-6:2014 (E) z height of centre of gravity; n exponent, open for scaling; c coefficient, open for scaling; ' 1st derivative in space domain; “ 2nd derivative in space domain; “' 3rd derivative in space domain; d distance between the rail head centres, equal to: - 500 mm for a nominal gauge of 435 mm; - 600 mm for a nominal gauge of 524 mm; - 740 mm for a nominal gauge of 668 mm Practical application on common track geometry data clearly shows that these formulas may be simplified as follows without loosing any significance: ay = c ⋅ v n ( AL' '+ z ⋅ ( LL" '− Ψ" )) a z = c ⋅ v n LL" ayz = ay + az Taking into account the different levels of aggregation mentioned in Clause it is recommended to average ayz over a distance of 100 m This figure or its standard deviation may be used for track geometry quality assessment A.4 Features of the PMA method — As the method is based on Newton’s second law the PMA assessment figure represents the accelerations which are needed to guide a point mass according to the above mentioned model Therefore the PMA method has a clear mechanical background — As the PMA model does not contain any vehicle specific features it cannot show any vehicle specific reactions, and therefore it is considered to be a vehicle independent assessment method — The PMA model takes into account the maximum line speed of the assessed track To achieve the same PMA track quality figure a track with a high maximum line speed needs to have lower geometrical imperfection than a track for a lower maximum line speed In this way one single limit value may serve for possibly all or at least a wide range of maximum line speeds — The derivatives of longitudinal level and alignment dominate the assessment figure Thus defects of the same amplitude but with different wavelengths lead to different assessment figures The correlation between the PMA assessment figure and wheel rail interaction forces is considered to be better than the correlation between the track geometry parameters as described in EN 13848-1 and wheel rail interaction forces — The PMA method gives just one quality figure for both vertical and lateral deviations as well as left and right rail of the track It takes into account the combination of isolated defects in longitudinal level and alignment 18 BS EN 13848-6:2014 EN 13848-6:2014 (E) Annex B (informative) Vehicle Response Analysis methods (VRA) B.1 Introduction This section deals with VRA methods based on numerical simulation using MBS (Multi Body System) vehicle models There exist other methods like neural networks, linear filters and other methods which are used in some commercial software packages In the following example a VRA method is described The vehicle models are used to determine a set of assessment functions that provide an estimation of the maximum vehicle response expectable for a number of different vehicle types passing the measured track section In the example presented here, the measured signals of longitudinal level, alignment and cross level are divided into single defects which are assessed sequentially taking the superposition of lateral and vertical track defects into account Input parameters of the assessment functions are the amplitudes and gradients of the separated single defects as well as the local permitted speed and the local curvature of the track The vehicle response parameters considered are: — sum of lateral guiding forces per wheelset: ΣY; — quotient of lateral and vertical contact forces per wheel: Y/Q; — maximum vertical wheel force: Qmax; — minimum vertical wheel force: Qmin; — maximum lateral car body acceleration: ay; — maximum vertical car body acceleration: az These parameters are normalized to their related limit values which are based on EN 14363 The output is for each measuring point the maximum of all calculated percentages of all considered vehicle types Hence this VRA method provides the maximum utilization of the limit value for the most critical vehicle response parameter of the most critical vehicle type B.2 Determination of the assessment functions For each vehicle type to be considered a set of assessment functions shall be determined This process is illustrated by the scheme shown in Figure B.1 In the first step several very detailed and well validated MBS vehicle models are used to simulate the vehicle response to a large number of variations of isolated track defects (test defects) in combination with different vehicle speed V and track curvature cr In curves the speed of the vehicle is chosen in order to reach the maximum permitted cant deficiency for the considered vehicle The track geometry is represented by the parameters longitudinal level (LL), alignment (AL) and cross level (CL) The test defects have a shape of a sine wave defined by: 19 BS EN 13848-6:2014 EN 13848-6:2014 (E) L − x , ≤ x ≤ L amp1 − cos 2π L y(x ) = otherwise where y isolated test defect; amp half amplitude of the isolated test defect; L defect length with systematically varying amplitudes and defect lengths covering the complete range of expected isolated defects Additionally different variants of superposition of lateral and vertical track defects are taken into account It shall be ensured that at least the limit values for the vehicle responses are reached The result of these simulations is the time signals of the considered vehicle response parameters which are filtered according to EN 14363 From these, the needed output values are obtained by normalizing the extreme values of the calculated vehicle response to the respective limit values The limit values should be based on EN 14363 but can be adapted according to the maintenance strategy Figure B.1 — Determination of the assessment functions In the second step for each vehicle response parameter i = 1, … and for each vehicle type k an assessment function of the form: Ri,k = ai,k + (bi,k ⋅ ALgr + ci,k ⋅ LLgr + di,k ⋅ CLgr + ei,k ⋅ ALamp + fi,k ⋅ LLamp + gi,k ⋅ CLamp) ⋅ V + hi,k ⋅ V ⋅ cr + ii,k ⋅ V + ji,k ⋅ |cr| 20 BS EN 13848-6:2014 EN 13848-6:2014 (E) shall be determined, with the indices “amp” indicating the amplitude and “gr” indicating the mean gradient of the test defects according to Figure B.2 The required coefficients of the assessment functions are calculated by solving the over-determined system of equations formed by the input parameters in combination with the related output values of the MBS simulations Figure B.2 — Definition of test defect parameters B.3 Application of the assessment functions For the assessment of track geometry measurements by this VRA method it is necessary to calculate the mean of left and right signals for both alignment and longitudinal level A possible weakening of the track defects due to the averaging is compensated by the scaling factor 1,2: AL* = 1,2 ⋅ (ALright + ALleft) / LL* = 1,2 ⋅ (LLright + LLleft) / Then the scaled signals AL* and LL* defined before as well as the original measured signal of cross level shall be divided into consecutive single defects which are defined as the section between two subsequent local extreme values of the signal (see Figure B.3) To avoid assessing too short and irrelevant wavelengths a minimum distance between the extreme values should be defined (e.g 1,0 m) Thereafter for each single defect of the AL*, LL* and CL* signals the characteristic parameters amplitude (amp) and gradient (gr) can be derived separately (according to Figure B.3) 21 BS EN 13848-6:2014 EN 13848-6:2014 (E) Figure B.3 — Division of the measured track geometry signals The two remaining input parameters needed for the evaluation of the assessment functions are the absolute value of the locally measured curvature of the track (cr) and the relevant vehicle speed (V) The relevant vehicle speed V is defined as the minimum of: — the local line speed vline; — the maximum permissible vehicle speed vlim; — the maximum speed in curves vcurve given by the designed cant D and the maximum permissible cant deficiency Iadm of the respective vehicle V = Min(vline, vlim, vcurve) with v curve = g (D + Iadm ) , d ⋅ cr where cr locally measured curvature of the track; g 9,81 m/s ; d 500 mm for nominal track gauge 435 mm NOTE The designed cant can be approximated by the local cant (e.g from low-pass filtered cross level) By means of these input parameters of the assessment functions determined before, all vehicle response parameters Ri,k representing the percentages of respective limit values can be calculated by: Ri,k = ai,k + (bi,k ⋅ AL*gr + ci,k ⋅ LL*gr + di,k ⋅ CL*gr + ei,k ⋅ AL*amp + fi,k ⋅ LL*amp + gi,k ⋅ CL*amp) V + hi,k V cr + ii,k ⋅ V + ji,k ⋅ |cr| The output of the VRA method is for each measuring point the maximum value of all estimated vehicle response parameters Ri,k Finally these output values can be analysed statistically to determine TQI values for a given track section depending on the selected level of aggregation 22 BS EN 13848-6:2014 EN 13848-6:2014 (E) B.4 Features of VRA methods — VRA methods use the relationship between track geometry and vehicle behaviour to assess the track geometry quality By means of analytical assessment functions the method provides an estimation of maximum vehicle response normalized by respective limit values where the superposition of lateral and vertical track imperfections in combination with the permissible vehicle speed and the resulting local cant deficiency is taken into account — VRA methods don't require any definition of speed classes because the relevant limit values of the vehicle responses are independent of the speed — In case of an exceedance of a defined limit value of vehicle response parameters, the limiting speed to be applied can be determined — The assessment functions can be selected according to the relevant vehicle types which are authorized to run on a considered track section 23 BS EN 13848-6:2014 EN 13848-6:2014 (E) Annex C (normative) Method for calculating reference TQIs (TQIref) C.1 Introduction According to subclause 7.1, standard deviation (SD) of longitudinal level and alignment calculated in D1 domain is taken as a reference to describe track geometry quality Hereafter, the complete method is described to calculate the reference TQI (TQIref) C.2 Description of the reference method The provided data for calculating reference TQIref shall include: — plain tracks of main lines, being outside or inside stations; — isolated switches or group of switches situated in main line and run at line speed Conversely, all side tracks should be excluded The calculation shall be done using standard deviation of longitudinal level SDLL and standard deviation of alignment SDAL in the domain D1 In the case where the origin of the measurement data are chord measurements, data shall be re-coloured to obtain D1 Data of left and right rail shall be averaged as a mean of the standard deviations of each rail as follows: SD LL = SDLL left + SDLL right SD AL = SDAL left + SDAL right where SD is the standard deviation; SD is the average of the standard deviations of each rail; LL is the longitudinal level; AL is the alignment The calculation of the standard deviation shall be done as follows: — The standard deviation is calculated over a distance of 200 m — The calculation is made at every measuring step, e.g 0,25 m — If a cumulative frequency distribution is determined, it shall be calculated for each speed range using classes of a resolution of 0,01 mm 24 BS EN 13848-6:2014 EN 13848-6:2014 (E) The data shall be separated into speed classes as follows: a) V ≤ 80 km/h; b) 80 km/h < V ≤ 120 km/h; c) 120 km/h < V ≤ 160 km/h; d) 160 km/h < V ≤ 230 km/h; e) 230 km/h < V ≤ 300 km/h; f) V > 300 km/h 25 BS EN 13848-6:2014 EN 13848-6:2014 (E) Annex D (informative) Method of classification of alternative TQI using the TQCs D.1 Introduction According to 7.1, standard deviation (SD) of longitudinal level and alignment is taken as a reference to describe track geometry quality For networks that not use the reference method as described in Annex C, an alternative TQI calculation method may be applied In this case, the relationship between the TQCs derived using this alternative TQI and the TQCs derived using the reference method may be established according to the method described below D.2 Description of the conversion method The conversion method described below is applicable for both longitudinal level and alignment, but if an alternative TQI is represented by a single value for vertical and lateral direction, the conversion should be based on SDLL The conversion method should be applied for each speed range In order to convert the alternative TQI into reference TQI (TQIref), the following information is required: — a cumulative frequency distribution of National TQIref (NTQI, dotted line in Figure D.1); — a cumulative frequency distribution of Alternative TQI (ATQI, dashed line in Figure D.1) Key cumulative frequency distribution of National TQIref (NTQIref) cumulative frequency distribution of Alternative TQI (ATQI) Figure D.1 — Translation between standard TQIref and alternative TQIs 26 BS EN 13848-6:2014 EN 13848-6:2014 (E) In order to convert one limit value of a TQC for a given speed range, the following steps should be done: — take the limit value from Table or Table 3, e.g class C, and find the corresponding percentage of the national cumulative frequency distribution of TQIref (NTQI, see point P1 in the Figure D.1); — read the ATQI value corresponding to the same cumulative percentage from the cumulative frequency distribution of the alternative TQI (ATQI, see point P2 in the Figure D.1) This ATQI value is the translation of the class limit chosen at the first step (e.g class C) 27 BS EN 13848-6:2014 EN 13848-6:2014 (E) Bibliography [1] FprCEN/TR 16513, Railway applications - Track - Survey of track geometry quality [2] EN 13848-5, Railway applications - Track - Track geometry quality - Part 5: Geometric quality levels - Plain line [3] EN 14363, Railway applications - Testing for the acceptance of running characteristics of railway vehicles Testing of running behaviour and stationary tests 28 This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards and other standards-related publications, information and services BSI is incorporated by Royal Charter British Standards and other standardization products are published by BSI Standards Limited About us Revisions We bring together business, industry, government, consumers, innovators and others to shape their combined experience and expertise into standards -based solutions Our British Standards and other publications are updated by amendment or revision The knowledge embodied in our standards has been carefully assembled in a dependable format and 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