High Speed Railways (HSR) is a hot topic in the Rail industry since the safer High Speed trains have proved the case. As many countries compete to build the High Speed Railways, developed countries are forced to upgrade the existing tracks to meet the need for speed. This article just analyses the conventional railways with HSR. Today, HSR’s speed, punctuality, and, above all, safety have not only achieved celebrated status among travellers throughout the world, but have fundamentally transformed passenger transport in several countries.

High-speed rail can mean many things, depending on context. For a traveler, HSR typically delivers comfort, speed, punctuality, safety and reliability just to begin—especially when journeying between central city businesses districts at a time of increasing airline delays.

Since its introduction in Japan in the 1960s, High Speed Rail has now become a worldwide phenomenon and investments are being developed to connect many of the world’s largest and growing cities. However, these nations’ decision makers face a complex array of choices in terms of technologies and operating systems and wrestle with adapting elements of established technologies to their local needs. Today, HSR remains a powerful symbol of a nation’s commitment to infrastructure.

 

What is HSR?

High-speed rail (HSR) is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. EC Directive 96/58 define high-speed rail as systems of rolling stock and infrastructure which regularly operate at or above 250 km/h on new tracks, or 200 km/h on existing tracks.

Current Speeds of HSR

It has been more than 50 years since the first high-speed rail (HSR) train captured the global imagination as it zipped past Mount Fuji 10 days before the opening of the 1964 Tokyo Olympics.

In Japan, Shinkansen lines run at speeds in excess of 260 km/h (160 mph) and are built using standard gauge track with no at-grade crossings. In China, high-speed conventional rail lines operate at top speeds of 350 km/h (220 mph). The world record for conventional high-speed rail is held by the V150, a specially configured version of Alstom’s TGV which clocked 574.8 km/h (357.2 mph) on a test run.

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Viability of HSR over Conventional Railways

High Speed Rail Operation can’t be carried out like conventional rail operation on classic lines. This is due to the high speed of the trains. Therefore, always a large amount of time is needed for a stop. Also the distances between the stops must increase in order to achieve a sufficient efficiency. The efficiency of a railway system means the quotient of commercial speed divided by the maximum speed of the Electric Multiple Unit (EMU) generating the commercial speed.

HSR can play an important role in a nation’s transportation network, depending on a range of demographic, geographic, social and economic factors. Determining when it is the right solution is as much an art as a science, requiring a view that balances local preferences with big-picture economic and engineering practicalities.

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While a host of weather events can severely disrupt both air and road transport, HSR often continues operating.

Safety is, finally, the most profound aspect of any transport mode’s “reliability”—and here HSR’s record is even more astonishing than its punctuality.

But the net economic costs of HSR’s social benefits, he argues, have to be weighed against the net costs and benefits of other investment.

Of course, the reality is that HSR is as viable as any other transport option, given all the costs— social, economic, and environmental—but that is not always clear to a public that must ultimately pay for a high-speed line’s construction.

In the end, choosing HSR requires careful study, balancing needs, expectations, and, above all, competing claims on public expenditures. Travellers around the world have embraced it.

Benefits of HSR

  • Time savings
  • Overcrowding relief
  • Net revenue
  • Environmental benefits

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Cost of HSR

In the UK, a new double track railway, like HS2, will cost around £76million per km.

A modern train will use up to £1.5million per vehicle.

Signalling systems will be up to £3million/km.

Power supplies and communications will fall into similar price ranges.

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HSR Operating Methods

Operating High Speed Rail (HSR) we can distinguish between two different kinds of Operation methods.

Operational Method 1: High speed EMU’s run exclusively over their own high speed tracks, which they don’t need to share with other trains. The fundamental reason for this state of affairs must be seen in the different gauge between the High Speed network and the classic network.

Operational Method 2: High Speed Trains (HST) also run, more or less, on classic lines.

Categories of HSR according European Union

– Category I: Specially built high-speed lines equipped for speeds generally equal to or greater than 250 km/h,

– Category II: specially upgraded high-speed lines equipped for speeds of the order of 200 km/h,

– Category III: Specially upgraded high-speed lines or lines specially built for high speed, which have special features as a result of topographical, relief, environmental or town

All categories of line shall allow the passage of trains with a length of 400 metres and a maximum weight of 1000 tonnes.

Interoperability of HSR

Interoperability simply means that technical specifications for HSR are harmonized on an EU-wide basis so that HSR can cross national boundaries. Since both France and Germany have made their HSR systems integrated and interoperable with their previously existing rail networks, this has resulted in the effective integration of German and French railway networks at the heart of a growing, Europe-wide HSR network.

Line Capacity:

Line capacity is the ability of a railway to carry a certain number of trains in one direction on one track over a certain period. It is determined by how many trains you can run on a track in this direction in an hour and is expressed as trains per hour (tph).

Line capacity will depend on

  • train performance, particularly braking and acceleration
  • train  length
  • Train Controlling system
  • the infrastructure
  • power availability
  • possible maximum line speed
  • the station spacing
  • the terminal design
  • the track gradients
  • the railway control (signalling) systems
  • dwell times at stations
  • terminal operations
  • allowances for speed restrictions

recovery margins

 

High-speed lines comprise:

– Specially built high-speed lines equipped for speeds generally equal to or greater than 250 km/h,

– Specially upgraded high-speed lines equipped for speeds of the order of 200 km/h,

– specially upgraded high-speed lines which have special features as a result of topographical, relief or town-planning constraints, on which the speed must be adapted to each case

Factors to consider on Line Speed

When designing a new or upgraded high-speed line, consideration should be given to other trains, which may be authorised on the line.

Rolling stock complying with the High-Speed Rolling Stock must be able to negotiate track compliant with limiting values set out in the present.

Infrastructure Interfaces:

From an infrastructure perspective the most significant issues are probably those relating to:

a) Structure gauge.

b) Overhead line interface.

c) Signalling equipment interface

Functional and technical specifications

 

The elements characterising the Infrastructure domain are

– Nominal track gauge

– Minimum infrastructure gauge

– Distance between track centres

– Maximum rising and falling gradients

– Minimum radius of curvature

– Track cant

– Cant deficiency

– Equivalent conicity

– Track geometrical quality and limits on isolated defects

– Rail inclination

– Railhead profile

– Switches and crossings

– Track resistance

– Traffic loads on structures

– Global track stiffness

– Maximum pressure variation in tunnels

– Effects of crosswinds

– Electrical characteristics

– Noise and vibrations

– Platforms

– Fire safety and safety in railway tunnels

– Access to or intrusion into line installations

– Lateral space for passengers and onboard staff in the event of detrainment outside of a station

– Distance markers

– Length of stabling tracks and other locations with very low speed

– Fixed installations for servicing trains

– Ballast pick-up

– Maintenance rules

List of basic parameters to consider in design

Line layout:
Structure gauge: The infrastructure must be constructed so as to allow safe clearance for the passage of trains complying with the High-Speed Rolling Stock.

Minimum infrastructure gauge is defined by given swept volume inside which no obstacle must be located or intrude. This volume is determined on the basis of a reference kinematic profile and takes into account the gauge of catenary and the gauge for lower parts. The structure gauge shall be set on the basis of the gauge set out for all the trains operate on the line. Calculations of the structure gauge shall be done using the kinematic method. Where overhead electrification is provided, the pantograph gauges are set out as well.

Distance between track centres:The nominal distance between track centres shall be 3 400 mm on straight track and curved track with a radius of 400 m or greater.

The distance between track centres shall be set on the basis of the gauge set out for the specific project. Where appropriate the minimum distance between track centres shall also take into account aerodynamic effects. Where appropriate the minimum distance between track centres shall also take into account aerodynamic effects.

Maximum gradients :  

Gradients as steep are permitted for main tracks at the design phase provided the ‘’envelope’’ requirements are observed. The design of gradients for new lines is a complex subject and needs to be considered with other system requirements. It is likely that any new high speed line needs to connect with the existing network.

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Minimum radius of horizontal curve: 

The minimum design radius of horizontal curve shall be selected with regard to the local design speed of the curve. When designing the lines for high-speed operation, the minimum radius of curvature selected shall be such that, for the cant set for the curve under consideration the cant deficiency does not exceed, when running at the maximum speed for which the line is planned

Minimum radius of vertical curve:

When designing the lines for high-speed operation, the minimum radius of curvature selected shall be such that, for the cant set for the curve under consideration the cant deficiency does not exceed, when running at the maximum speed for which the line is planned

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Track parameters:
Nominal track gauge :  

Nominal Track gauge is mostly fixed to standard value and for Europe is always 1435 mm

Cant :

The highest cant on a section of line shall be published in the Register of Infrastructure. The design cant on tracks adjacent to station platforms are limited.

Rate of change of cant (as a function of time) :The design of cants for new lines is a complex subject and needs to be considered with other system requirements.

The maximum rate of change of cant through a transition shall be calculated at the maximum speed permitted for trains not fitted with a cant deficiency compensation system. The design of cants for new lines is a complex subject and needs to be considered with other system requirements.

Cant deficiency: In curves, cant deficiency is the difference, expressed in mm, between the applied cant on the track and the equilibrium cant for the vehicle at the particular stated speed. The maximum cant deficiency at which trains are permitted to run shall take account of the acceptable criteria of the vehicles concerned.

The design for maximum cant deficiency for new lines is a complex subject and needs to be considered with other system requirements for the project.

Equivalent conicity : The wheel-rail interface is fundamental to explaining the dynamic running behaviour of a railway vehicle. It needs therefore to be understood and, among the parameters by which it is characterised, the one called equivalent conicity plays an essential role since it allows the satisfactory appreciation of the wheel-rail contact, on tangent track and on large-radius curves.

Design values of track gauge, rail head profile and rail inclination for plain line shall be selected to ensure that the equivalent conicity limits

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Railhead profile for plain line :

The design of railhead profiles for plain line shall comprise:

  • a lateral slope on the side of the railhead angled to between vertical and reference to the vertical axis of the railhead;
  • a minimum radius of at at the gauge corner;
  • a range of horizontal distance between the crown of the rail and the tangent point
  •  a defined vertical distance between the top of this lateral slope and the top of the rail

Rail inclination:

The rail shall be inclined towards the centre of the track. The nominal rail inclination for the GB network is 1/20. If a different nominal value is selected then compatibility with the existing network will be difficult to achieve and through running of vehicles could give rise to problems.

Track stiffness:

Requirements for track stiffness as a complete system are an open point.

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Switches and crossings

Requirements for switches and crossings

– The rail in switches and crossings shall be designed to be either vertical or inclined.

-If the rail is inclined, the designed inclination in switches and crossings shall be the same as for plain line.

-The inclination can be given by the shape of the active part of the rail head profile.

– For short sections of plain line between switches and crossings without inclination, the laying of rails without inclination is permitted.

– A short transition from inclined rail to vertical rail is permitted.

Means of locking: All movable parts of switches and crossings shall be equipped with a means of locking, except in marshalling yards and other tracks used only for shunting.

In-service geometry of switches and crossings: Assessment of switches and crossings at the design phase is required to verify that the design values used are consistent with the in-service limiting values

Maximum unguided length of fixed obtuse crossings: Calculating and comparing the unguided length is not easy because several parameters are included within each of the assessment methods. Some of these parameters are common to both methods however, at least one is not, for example raised check rails are not generally used in GB and therefore are not considered in the UK low speed rule.

Track resistance to applied loads

 

Track resistance to vertical loads: The track, including switches and crossings, shall be designed to withstand at least the following forces:

  • the axle load
  • the maximum dynamic wheel force exerted by a wheelset on the track.
  • the maximum quasi static wheel force exerted by a wheelset on the track.

Longitudinal track resistance: Track shall also be designed to withstand the longitudinal thermal forces arising from temperature changes in the rail and to minimise the likelihood of track buckling. The track, including switches and crossings, shall be designed to withstand longitudinal forces arising from braking.

Lateral track resistance:

The track, including switches and crossings, shall be designed to withstand at least:

  • the maximum total dynamic lateral force exerted by a wheelset on the track.
  • the quasi static guiding force exerted by a wheelset on the track.

 

Structures resistance to traffic loads

Resistance of new bridges to traffic loads:Vertical loads: Structures shall be designed to support vertical loads in accordance with the Eurocodes (EN 1991-2:2003)Nosing forces: The nosing forces shall be taken into account in the design of structuresTraction and braking forces shall be taken into account in the design of structures: The maximum total design track twist due to rail traffic actions shall not exceed the values set out in the standards.

Actions due to traction and braking (longitudinal loads): Traction and braking forces shall be taken into account in the design of structures

Centrifugal forces: Where the track on a bridge is curved over the whole or part of the length of the bridge, the centrifugal force shall be taken into account in the design of structure.

Dynamic analysis: The need for a dynamic analysis on bridges shall be determined

Equivalent vertical loading for new earthworks and earth pressure effects:

Assessment of structures is to be made by only checking the traffic loads used for design. Earthworks shall be designed to support vertical loads

Resistance of new structures over or adjacent to tracks:

Aerodynamic actions from passing trains shall be taken into account for the structures next to track

Resistance of existing bridges and earthworks to traffic loads Assessment of existing structures is to be made against new loadings.

Track geometrical quality and limits on isolated defects

 

Track geometrical quality and limits on isolated defects are important infrastructure parameters, needed as part of the definition of the vehicle-track interface. The geometrical quality of the track is directly linked to:

– Safety against derailment

– Assessment of a vehicle according to acceptance tests.

– Fatigue strength of wheelsets and bogies.

Determination of immediate action, intervention, and alert limits:

Lateral alignment

  1. Variation of track gauge
  2. Longitudinal level
  3. Longitudinal level:
  4. The infrastructure manager shall determine appropriate immediate action, intervention and alert limits for the following parameters:
  5. The immediate action limit for track twist:
  6. The immediate action limit for track twist as an isolated defect is given as a zero to peak value. Track twist is defined as the algebraic difference between two cross levels taken at a defined distance apart, usually expressed as a gradient between the two points at which the cross level is measured. The cross level is measured at the nominal centres of the rail heads.

The immediate action limit for variation of track gauge: The immediate action limits for variation of track gauge are defined in standards.

The immediate action limit for cant: The in service cant shall be maintained respect to design cant

Platforms

Usable length of platforms

Width and edge of platforms

End of platforms

 Height of platforms

 Offset of platforms

 

Health, safety and environment

 

 

Noise and vibration limits and mitigation measures

The environmental impact of the projects concerning the design of a line specially built for high-speed or on the occasion of line upgrading for high-speed shall take into account noise emission characteristics of the trains complying with the High-Speed Rolling Stock at maximum speed.

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Protection against electric shock

Safety in railway tunnels

 

Maximum pressure variation in tunnels: 

The maximum pressure variation in tunnels and underground structures along the outside of any train complying shall not exceed design pressue during the time taken for the train to pass through the tunnel, at the maximum permitted speed.

Effect of crosswinds:

Vehicles are designed to ensure a certain level of cross wind stability, which is defined within High-Speed Rolling Stock TSI by a reference set of characteristic wind curves.

 

 

Provision for operation

Distance markers: Distance markers shall be provided at periodical intervals along the track. The provision of distance markers shall be in accordance with national rules.

Fixed installations for servicing trains

Toilet discharge: Fixed installations for toilet discharge shall be compatible with the characteristics of the retention toilet system specified in the rolling stock standard.

Train external cleaning facilities: When washing machines are used they shall be able to clean the outer sides of single or double-deck trains between a height of:

– 500 to 4 300 mm for double-deck trains

– 1 000 to 3 500 mm for a single-deck train

Water restocking: Fixed equipment for water supply on the interoperable network shall be supplied with drinking water meeting the requirements

Refuelling: Fixed equipment for water supply on the interoperable network shall be supplied with drinking water meeting the requirements

Electric shore supply

About the Author :

Sujay Sujatharan

Sujay is an experienced Railway Engineer. He worked in Major Railway projects in UK including Crossrail , London Underground and Great Western Modernisation. Sujay has good experience in Integrated Railway Design and Interface Management.

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