track standards manual - track geometry

This document is the property of Railtrack PLC. It shall not be reproduced in whole or in part without the written permission of the Controller, Railway Group Standards, Railtrack PLC. Published by Safety & Standards Directorate, Railtrack PLC, Floor DP01, Railtrack House, Euston Square, London NW1 2EE © Copyright 1998 Railtrack PLC

Railway Group Standard

GC/RT5017 Issue Two Date December 1998

Track Standards Manual - Section 8: Track Geometry

Synopsis This section of the Track Standards Manual sets down the minimum requirements for design, inspection and maintenance relating to track geometry of the permanent way forming part of Railtrack’s infrastructure.

Submitted by

Patricia Dingwall Standards Project Manager

Authorised by

Richard Spoors Controller, Railway Group Standards

Withdrawn Document Uncontrolled When Printed

This page has been left blank intentionally


Track Standards Manual - Section 8:

Track Geometry

R A I L T R A C K 1


GC/RT5017 Issue Two Date December 1998 Page 1 of 14

Contents Section Description Page

Part A

Issue Record 2 Responsibilities and distribution 2 Implementation 2 Health and Safety Responsibilities 2 Supply 2

Part B

1 Purpose 3 2 Scope 3 3 Definitions 3 4 Principles 4 5 Requirements 5 6 Normal Limiting Values 6 7 Exceptional Design Values 7 8 Maximum Speed Assessment 8 9 Radius on S&C 8 10 Track Geometry Recording 9

Appendix

A Equations 12

References 14



2 R A I L T R A C K



Part A Issue Record

This Standard will be updated when necessary by distribution of a complete replacement.

Amended or additional parts of revised pages will be marked by a vertical black line in the adjacent margin.

Issue Date Comments 1 September 1995 Original Document 2 December 1998 Revised document This Standard forms part of GC/RM5600 'Track Standards Manual'.

Responsibilities and Distribution

This Standard shall be complied with by all persons who are responsible for the design, installation, inspection and maintenance of the track geometry on Railtrack controlled infrastructure *The Railway Group comprises Railtrack and the duty holders of the Railway Safety Cases accepted by Railtrack

Implementation The provisions in this Railway Group Standard are to be complied with from 6th February 1999, with the exception of Clauses 5.6 and 5.9 which shall be February 2001 and Clause 5.13 which shall be February 2004.

Health and Safety Responsibilities

Railtrack PLC makes no warranties, express or implied, that compliance with all or any of Railway Group Standards is sufficient on its own to ensure safety systems of work or operation. Each user is reminded of its own responsibilities to ensure health and safety at work and its individual duties under health and safety legislation.

Supply Controlled and uncontrolled copies of this Standard may be obtained from the Industry Safety Liaison Dept, Safety and Standards Directorate, Railtrack PLC, Railtrack House DP01, Euston Square, London, NW1 2EE.



Track Geometry

R A I L T R A C K 3



Part B 1 Purpose

The purpose of this Standard is to define the requirements for track geometry in terms of the management of horizontal and vertical alignment, in connection with curvature and permitted line speeds.

It sets out the minimum inspection frequencies and the minimum actions to be taken upon discovery of non-conformance with track geometry standards.

2 Scope The contents of this Standard apply to all running lines and sidings on Railtrack controlled infrastructure.

3 Definitions CIRCULAR CURVE A curve of constant radius.

TRANSITION CURVE A curve of varying curvature. It is normally provided between two Circular curves, each of different radius, or between a Circular curve and a Straight.

COMPOUND CURVE A curve which is formed from similar flexure curves of different radii, which may be connected by Transition Curves.

REVERSE CURVE A curve formed by two Circular Curves, which curve in opposite directions and which may be connected by Transition Curves.

HORIZONTAL CURVE A curve in the track used to join two alignments in plan.

REVERSE POINT The point of infinite radius at which two curves of opposite flexure meet.

VERTICAL CURVE A curve in the longitudinal profile of track used to join two gradients together.

CANT The amount by which one running rail is raised above the other running rail; measured at the centre of the rail head (It may be expressed as a difference in height or in terms of an angle).

Cant is positive when the outer rail on a curve is raised above the inner rail and is negative when the inner rail is raised above the outer rail.

Negative Cant may be unavoidable at S&C on a Canted main line where the turnout is curving in the opposite direction (contra flexure) from the main line or at the plain line immediately adjoining the turnout.

EQUILIBRIUM SPEED The speed of a vehicle following a curved path is such that the resultant of the weight of the vehicle and the effect of centrifugal force is perpendicular to the plane of the rails.

EQUILIBRIUM CANT The amount that it is necessary to raise one running rail above the level of the other running rail to obtain Equilibrium at a nominated speed.

CANT DEFICIENCY The difference between actual Cant and the theoretical Cant that would have to be applied to maintain Equilibrium at a nominated speed (Cant deficiency is expressed in the same terms as cant).



4 R A I L T R A C K



PERMISSIBLE SPEED The speed which may be permitted on a curve with associated transitions when radius, Cant, Cant Deficiency, Cant gradient and rates of change of Cant and Cant Deficiency have all been taken into consideration together with the characteristics of the trains. When the Permissible Speed of the curve or part of the curve is less than the route speed limit for the particular type of train it will be necessary to impose a lower Permanent Speed Restriction at that location.

LINE SPEED LIMIT The maximum speed at which traffic is allowed to run on a line or on sections of a line. The Line Speed Limit is usually established after taking into consideration the incidence of permanent speed restrictions and the type of traffic on the line.

TRACK GRADIENT The distance travelled horizontally for a rise of one unit (expressed as 1 in X, where X is the distance travelled horizontally. (May be expressed in terms of an angle or a percentage.)

CANT GRADIENT The amount by which Cant is increased or decreased in a given length of track, e.g. 1 in 1200 means that a Cant of 1mm is gained or lost in every 1200mm of track.

RATE OF CHANGE OF CANT OR RATE OF CHANGE OF CANT DEFICIENCY The rate at which Cant or Cant Deficiency is increased or reduced relative to the maximum speed of a vehicle passing over the Transition Curve, e.g. 35mm per second means that a vehicle when travelling at the maximum speed permitted will experience a change in Cant or Cant Deficiency of 35mm in each second while travelling over the length of transition.

TRACK TWIST The variation in cross level over a given distance along the track. It has the same value as Cant Gradient, except the term Track Twist is normally associated with higher values which are considered to be faults.

4 Principles 4.1 The horizontal and vertical geometry shall be designed according to the normal train operating speed.

4.2 The track geometry shall be measured and recorded at a periodicity based on the expected deterioration of the track and the minimum requirements to prevent the track deteriorating into a condition which may cause:

derailments unacceptable clearances a risk of injuries from uneven ride, etc.

4.3 Upon discovery of substandard track, corrective action shall be carried out within timescales which are based on expected further deterioration and which will prevent an unsafe condition occurring.

4.4 Where this Standard refers to ‘Railtrack’ this will have the meaning of the Railtrack Line organisation at Zone level responsible for compliance with Railway Group and Corporate Standards.



Track Geometry

R A I L T R A C K 5



5 Requirements 5.1 On running lines, Horizontal Curves shall consist of one or more Circular Curves. They must be connected to the adjacent curved or straight track by a Transition Curve to meet the Rate of Change of Cant and / or Cant Deficiency requirements.

5.2 Cant shall be designed and maintained such that:

the lateral forces and variation in loading on both rails is minimised for the expected traffic on the route, and

there is no risk of vehicles overturning when travelling at maximum speed or when stationary.

5.3 Cant and alignment design affecting structural or passing clearances shall take account of the requirements of GC/RT5204.

5.4 Cant shall increase or decrease in proportion to curvature over the whole length of the Transition Curve between two Circular Curves or between a Circular Curve and straight track and shall be specified in multiples of 5mm. It shall take into account:

permitted Line Speed Limit; relative importance and speeds of the various types of traffic using the line.

5.5 The Cant on each track of a double or multiple line shall be considered separately.

5.6 The maximum Cant on sharp radius curves shall not be greater than shown in the following table.

Radius in metres Maximum Applied Cant in mm 200m 150 mm 200m but 150m 100 mm 150m but 100m 50mm 100m 25mm

5.7 When switches and crossings are located on curved track, the Cant to be applied on the through line shall not cause the maximum permitted value of negative Cant to be exceeded on a turnout of contra flexure.

5.8 All new sidings, whether straight or curved shall, where reasonably practicable, be laid without Cant and the Track Gradient of standing sidings shall not be steeper than 1 in 500.

5.9 Horizontal Curves shall be designed to take account of the curving characteristics of the vehicles likely to use the track but shall not be less than 120m radius on passenger running lines.

The normal minimum radius on non-passenger running lines and sidings is 90m. (70m with Railtrack permission)

Records shall be kept of all locations with curves below 90m radius.



6 R A I L T R A C K



5.10 The minimum radius of each Curve meeting at a Reverse Point on a passenger running line is 140m and for non-passenger lines and sidings is 120m. Abutting Curves of opposite hands, where one curve is less than 160m radius, shall be connected by straight track of length equal to or greater than the wheel base of the longest vehicle likely to use the line, or transitions installed, to prevent horizontal buffer locking. There are no extra requirements for Compound Curves.

5.11 The relative levels of adjacent tracks shall be designed to maintain adequate ballast shoulders as required for stability.

5.12 The track shall be maintained such that twists worse than 1 in 200 are managed. The timescales for the required actions where such faults occur are specified in 10.2.2.

5.13 Records of all Track Gradients and horizontal curves on running lines shall be maintained. Details to be recorded shall include:

cants; transition details; radius; maximum allowable speeds for various rolling stock types likely to use the

route.

Vertical curves below 1Km radius shall also be recorded.

6 Normal Limiting Values

The Normal Limiting design values, which are compatible with the inspection and maintenance requirements specified in Railway Group Standards, are as follows:

6.1 Cant: 150mm; Cant within station platforms: 110mm; Cant on fixed obtuse crossings: 110mm.

6.2 Negative Cant shall not be installed except on or adjacent to S&C where the values are:

65mm for fixed obtuse crossings and; 80mm elsewhere.

6.3 Cant Gradient: 1 in 400. The following effects shall be taken into account when proposing to install cant gradients approaching this value:

effect of top planing of crossing noses at the point of load transfer through switches and crossings;

deflection on skew underbridges.



Track Geometry

R A I L T R A C K 7



6.4 Swing nose crossings shall not be installed on a Cant gradient.

6.5 Rate of Change of Cant: 55mm/sec.

6.6 Cant Deficiency:

Jointed Track : 90mm; CWR : 110mm.

(see also clause 9.1).

6.7 The Rate of Change of Cant Deficiency on plain line, on all inclined S&C and on the through tracks of vertical S&C: 55mm/sec.

The Rate of Change of Cant Deficiency elsewhere on vertical S&C: 80 mm/sec. The rate of change at the switch toes can be disregarded.

6.8 Vertical radii (concave and convex): 1 km

Vertical acceleration experienced in a vehicle : 0.06g. An equation for calculating radii is given in Appendix A.

6.9 Track Gradient 1:40

7 Exceptional Design Values

It shall be permissible to use exceptional design values provided that any increase in risk is assessed and managed. Railtrack shall maintain records of the assessments used.

7.1 Track Gradient : 1:25

Design of Track Gradients shall take account of interfaces which include:

vehicles (braking and power); signalling requirements; maintenance regime.

7.2 Cant on plane line : 180mm; Cant within station : 130mm.

7.3 Cant Deficiency on plain line jointed track may be up to 110mm for suitably approved rolling stock only e.g. Class 15x “Sprinters”.

Cant Deficiency on plain line CWR for “Passenger” rolling stock (as defined in GO/RT3000) provided that no S&C, catch points, adjustment switches, level crossings or other features likely to contribute to lateral misalignment are situated on the transition or curve: 150mm



8 R A I L T R A C K



7.4 Rate of Change of Cant on plain line: 85mm/sec.

7.5 The Rate of Change of Cant Deficiency on plain line, on all inclined S&C and on the through tracks of vertical S&C: 70mm/sec.

(The Rate of Change of Cant Deficiency elsewhere on vertical S&C remains the same as in 6.7.)

7.6 Radius of vertical curves in passenger lines, (where there is at least 30m constant gradient between reverse Vertical Curves and the maximum acceleration rate specified in clause 6.8 is observed: 500m.

Radius of Vertical Curves in non - passenger running lines and sidings: 200m. The ability of the rolling stock to transverse the Vertical Curves shall include consideration of:

vertical buffer locking coupling / interconnection designs under clearances

7.7 For trial or evaluation purposes it shall be permissible to exceed the requirements specified in sections 5, 6, 7 and 8 where any necessary enhancements (based on risk assessments) to the inspection, maintenance and other requirements specified in Railway Group Standards have been approved by Railtrack and are being adhered to.

8 Maximum Speed Assessment

The Permissible Speed of trains on a curve of given radius and Cant shall take into account the radius of the curve, applied Cant, Cant Deficiency, Cant Gradient and rates of change of Cant and Cant Deficiency. The maximum speed equation is specified in Appendix A. Maximum speeds shall be rounded to the nearest multiple of 5 mph relative to the calculated maximum speed.

9 Radius on S&C 9.1 Switches The theoretical Cant Deficiency at the toes of switches shall not exceed 125mm. In order to assess the maximum permitted speed it is necessary to calculate the radius at the switch toes. The radius shall be obtained by calculating the offset at the toes based on a 12.2m chord centred about the switch toe. An equation is given in Appendix A.

9.2 Turnouts - Diverging and Converging Where the main line is curved, the turnout radius shall be used for the determination of speeds through the turnout. An equation is given in Appendix A.

10 Track Geometry Recording

10.1 Frequencies Track geometry recording frequencies are based on the Track Category Matrix as defined in the Track Standards Manual - Section 1: Basic Track Category Matrix GC/RT5023.



Track Geometry

R A I L T R A C K 9



0

50

100

150

0 10 20 30 40 50 60

SPEEDmph

Cat 1

Cat 4

Cat 2Cat 3

Cat5

Cat6

140

EQUIVALENT MILLION GROSS TONNES PER ANNUM

10.1.1 The track geometry shall be recorded, using a Railtrack approved track geometry recording vehicle, at intervals as specified in the following table or at a greater frequency if the condition of the track is such that the recommended frequency is insufficient to prevent an unsafe condition occurring.

Track Category Nominal interval (months)

Maximum interval (months)

1 3 4 2 6 8

3, 4, 5, 6 12 14

10.1.2 Lines with a maximum speed of 20mph or less need not be recorded, unless carrying dangerous goods, in which case the route shall be inspected by manual methods approved by Railtrack or by a Railtrack approved track geometry recording vehicle.

10.1.3 It is accepted that not all running loops, platform lines, station throats and crossovers can be recorded at the required frequencies. It is therefore essential that when a recording is made the results are examined closely and any sections not recorded are noted. Increased inspections using manual measurements shall be considered on such lengths of track.



1 0 R A I L T R A C K



10.2 Recordings 10.2.1 Track Quality Measurement The following shall be measured:

3m and 5m twists; the vertical profile of the rails, filtering out wave lengths greater than 35

metres; the alignment of the rails, filtering out wave lengths greater than 35 metres.

Standard Deviation ( ) must be calculated using the Standard Deviation equation in appendix A.

The maximum permitted standard deviations in mm are as follows:

LINESPEED (mph)

35 metre vertical profile

35 metre alignment

10 - 20 8.3 9.3 25 - 30 7.7 8.6 35 - 40 7.2 7.9 45 - 50 6.7 7.3 55 - 60 6.3 7.0 65 - 70 6.0 6.7 75 - 80 5.7 6.3 85 - 95 5.3 6.0

100 - 110 5.0 5.7 115 - 125 4.7 5.0 130 - 140 4.4 4.7

Note: These values are for eighth mile sections.

Where standard deviations are greater than those specified in the table, appropriate action shall be taken to either improve the track geometry or the linespeed must be reduced to a level where the standard deviation is below the maximum permitted.

10.2.2 Exceedence Limits In addition to the measurements required for the above calculations, sufficient measurements shall be made to enable any isolated irregularities to be identified. If any of the irregularities listed below are discovered, the stated action shall be carried out within the specified time scales:

IRREGULARITIES ACTION

Dynamic Twist of 1 in 90 or worse Stop all traffic immediately

Dynamic Twist between 1 in 91 and 1 in 125

Correct within 36 hrs. of recording

Dynamic Twist between 1 in 126 and 1 in 199

Correct within 10 working days of recording

Variation in cyclic top of 20 mm Inspect, assess risk and apply appropriate temporary speed restriction.

The stated actions are where the irregularities are occurring in track with no other significant faults. Where there are other faults known, an assessment shall be carried out, and where required, more stringent action taken.



Track Geometry

R A I L T R A C K 1 1



The corrective action taken and date completed must be recorded. Records shall be retained for 2 years for audit purposes.

10.3 Railtrack shall ensure that all reports of track condition are received by the relevant infrastructure contractor in sufficient time for any remedial work to be carried out in accordance with any required minimum actions.






Appendix A Equations

1. Permissible Speed

VR E D

( )

.1182

When V = speed (kph) R = radius of curve (m)

E DV

R

1182 2.

E = applied Cant (mm) D = Cant Deficiency (mm)

2. Standard Deviation

11

2m a a( )

where: a = mean value a1 = sample value

m = total no. of values

3. Effective Radius - Switches

RC

V

2

8

where:

R = radius C = chord (12.2 metres) central about the switch toe V = versine



Track Geometry

R A I L T R A C K 1 3



4. Effective Radius - Turnouts diverging with contra flexure

RR R

R Rem

m

Where

Re = effective radius Rm = radius of main line RT = radius of turnout curve

5. Effective Radius - Turnouts diverging with similar flexure

RR R

R Rem

m

Where

Re = effective radius Rm = radius of main line RT = radius of turnout curve

6. Vertical Radius for an acceleration rate of 0.06g

RV

=2

7628

Where R = radius in km and V = speed (kph)






References

GC/RT5204 Structure Gauging and Clearances

GC/RT5023 Track Standards Manual - Section 1: Basic Track Category Matrix

GO/RT3000 The Master Rule Book


track standards manual - track geometry

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