The Railway Track and Its Long Term Behaviour

The idea of using ”tracked” roads is at least 2000 years old. Ancient civilisations realised that wheeled vehicles ran more efficiently and needed less maintenance if they were guided using grooves cut into the stone blocks of roads. Quarries in Ancient Greece, Malta and the Roman Empire used cut stone tracks to haul loads pulled by animals.

Wagon ways (or ’tramways’) are thought to have developed in Germany in the 1550s to facilitate the transport of ore tubs to and from mines, utilising primitive wooden rails (Figure 4). Such an operation was illustrated in 1556 by Georgius Agricola. These used the “hund” system with unflanged wheels running on wooden planks and a vertical pin on the truck fitting into the gap between the planks, to keep it going the right way. Such a transport system was used by German Miners at Caldbeck, Cumbria, perhaps from the 1560s.

In medieval times people mostly travelled on foot or horseback and any form of transportation was mainly for moving goods.

The first railways were laid down in the seventeenth and eighteenth century for horse drawn trains of wagons in collieries and quarries. These ‘hauling ways’ initially had a surface of stone slabs or timber baulks, which soon proved unsatisfactory as the loads carried inevitably grew heavier.

James Watt, a Scottish inventor and mechanical engineer, was responsible for improvements to the steam engine of Thomas Newcomen, before used to pump water out of mines. Watt developed a reciprocating engine, capable of powering a wheel. Although the Watt engine powered cotton mills and a variety of machinery, it was a large stationary engine.

In January 1888, Richmond, Virginia served as a proving ground for electric railways as Frank Sprague built the first working electric streetcar system there. By the 1890s, electric power became practical and more widespread, allowing extensive underground railways. Large cities such as London, New York, and Paris built subway systems. When electric propulsion became practical, most street railways were electrified. These then became known as ”streetcars,” ”trolleys,” ”trams” and ”Straßenbahn.” They can be found around the world.

Starting with the opening of the first Shinkansen line between Tokyo and Osaka in 1964, high-speed rail transport, functioning at speeds up and above 300 km/h, has been built in Spain, France, Germany, Italy, the People’s Republic of China, Taiwan, the United States, the United Kingdom, South Korea, Scandinavia, Belgium and the Netherlands. The construction of many of these lines has resulted in the dramatic decline of short haul flights and automotive traffic between connected cities, such as the Boston-New York City-Washington, D.C. corridor, London-Paris-Brussels, Madrid-Barcelona, as well as many other major lines. Additionally, with the on-going threat of global warming and energy shortages, high-speed rail is supposed to hold the key to the future of transportation in many of the world’s developed countries.

Historically, the choice of gauge was partly arbitrary and partly a response to local conditions. Narrow-gauge railways are cheaper to build and can negotiate sharper curves but broad-gauge railways give greater stability and permit higher speeds.

The Infrastructure Manager has to act in an increasingly challenging external environment. There are various stakeholders who have interests in the activities of the railway Infrastructure Manager. The available government budgets are decreasing, and at the same time there are increased needs for higher infrastructure capacity utilisation. An efficient way of managing the rail infrastructure is required.

In Europe the environment for the rail Infrastructure Managers, is changing:

new European directives (in the European Union influence zone),

decreasing government budgets,

need for higher infrastructure capacity utilisation and

increasing customer expectations.

This change requires a very efficient way of managing the rail infrastructure maintenance activities.

Multi-annual contracts represent a long-term financing arrangement between the State and the rail Infrastructure Manager for infrastructure maintenance. Multiannual contracts should force both parties to take a long-term view and develop maintenance plans on the basis of the infrastructure manager’s business plan and thus on future service demand.

A “system” can be defined as a complex of elements standing in interaction. Systems thinking involves inter alias shifting attention

from the parts to the whole,

from objects to relationships,

from structures to processes

When we use systems thinking, we are actively asking ourselves

“Why is this working as it does

?”

The railway system is a very complex system: it is often a mixture of components of different age and status that have to work together in a system. The railway track has to guide the trains in a safe and economic manner. The track and the switches should allow smooth passage of the trains [24][24.1].

Both vehicle and track have irregularities

track geometry irregularities (long wavelength) or

discrete irregularities (short wavelength) in the wheel tread or rail running surface.

These two classifications of track irregularities (long/short wavelength) produce different magnitudes of forces due to the resonances they create within the track structure.

The railway track has to fulfil two main functions:

to

guide the train

with safety

to

carry the load

of the train and to

distribute

the load to the subgrade over an area that is as large as possible.

Today there is a general trend towards increased train speeds (see also SECTION II). However, higher speeds usually generate increased forces and accelerations on the vehicle and subsequently forces on the track. This leads to requirements for lighter car bodies, which reduce the impact between wheels and rails. However, lowering the car-body weight also means a reduction of the stiffness of the vehicle structure, which results in lower natural frequencies. This increases the risk of resonance vibrations, which negatively affects ride comfort. Car body vibrations can be reduced either by focussing on the structural stiffness of the system or by optimizing the damping components ([56]).

The railway system can be considered as an assembly of structural components with specific mechanical properties. They are characterised by their frequency response function which is directed by mass elastic properties. These parameters define the frequencies at which the structure is likely to vibrate [9].

What is track stiffness? There is not a complete consensus on definitions of track stiffness. The most general understanding defines track stiffness as the elastic rail deflection that takes place under a wheel loading.

The wheel/rail contact determines the capabilities of the railway system. This contact is the critical point at high speeds and in cases of heavy freight trains with high axle load, due to the high contact forces and the dynamics, but it is also responsible for noise emissions and wear (Figure 44).

Deterioration or degradation is the

reduction of the original quality due to various influences

.

By far the most significant factor contributing to the deterioration is the dynamic load. The dynamic load is directly related to the axle load and track geometry.

The track is composed of several components as presented in previous paragraphs. Each component has a specific function. The track experiences vertical, horizontal, and longitudinal forces, as described in Chapter 12.

These forces influence the functions of the basic components in the track which in turn affect degradation and the failure process. The failure of each component has an effect on the function of other components in the track system (Figure 67).

Railway track will settle due to the permanent deformation in the ballast and underlying soil.

A new track is straight and well levelled. After having been used some time, the track loses its perfect track geometry due to the train traffic. The severity of the settlement depends mainly on the quality and the behaviour of the ballast, the sub-ballast, and the subgrade.

Wheel/rail contact happens over a very small area (see Chapter 17). In this small area the stresses can cause a variety of defects. Defects or irregularities in either wheel or rail generate sharp peak forces (high frequency forces) in the vehicle and the track (par. 17.7).

The failure of manganese diamonds (crossings) is analogous to wear in switches and therefore these priorities are equally relevant for cracked diamond (crossing)s.

A switch forms a discontinuity in any track where one is installed. It is a discontinuity with regards to track support due to the altered sleeper arrangement and during tamping operations it may require a separate operation or manual correction. A switch also forms a discontinuity for the wheel rail contact patch that may give rise to high transient vertical and creep forces (see 17.6.3.3). The high lateral accelerations to any vehicle not travelling in the straight ahead position will also cause high forces. The installation and maintenance of a switch is critical to its performance and any error may not be immediately apparent. For all these reasons, a switch will experience higher forces than plain line and the life of the switch will generally be reduced by plastic deformations, wear and/or fatigue cracks ([24][24.3])

There are four principal sources of water to consider that can affect the track [78]:

1

Rainfall directly on the track structure.

2

Surface water flowing toward and infiltrating the track structure.

3

Water flowing within the track structure, e.g., within ballast pockets (par. 19.6.2) or fill used to construct the embankment.

4

Groundwater.

It is well known that deterioration depends on the present quality level:

good track behaves well (deteriorates more slowly),

poor one deteriorates faster

The system “railway infrastructure” can be described by three basic constituents: the capacity of the network, the substance and the quality of infrastructure (Figure 114) [77]:

Capacity

(maximal number of operable and marketable train-paths in a given time span, on a given part of the network),

Substance

(average remaining life time of infrastructure components) and

Quality

(quality of track’s geometry and of its components).

There are general questions referring to track quality, which are dominant in periods with big budget constraints:

Do we really need quality?

How much quality is technically necessary?

Is quality economically justified?

As we examined in Section IV, “deterioration or degradation is the reduction of the original quality due to use and/or environmental influences”. In par. 18.2 we identified that three main groups of factors may be distinguished that contribute to the deterioration of railway infrastructure:

Use:

wear by physical contact, static and dynamic load

Environment:

climatic influence, water

Failures:

faulty components, bad construction

In most of the cases it is not just one of these factors that causes deterioration, but a combination of them.

The condition of the superstructure is described by

1

The track quality

2

The amount and the severity of speed restrictions (speed decrease over a length)

3

Track positions with long lasting problems

Track geometry is normally measured by track recording cars. They enable the standard deviations to be calculated, which have proved to be useful for describing the track quality. In some cases, also vehicle reactions calculated from the recorded geometry are used to assess track quality.

For many centuries, buildings and other structures were designed using common sense, trial and error, and rules of proportion acquired through experience. Their effectiveness depended on the knowledge and skills of master craftsmen.

As we examined in Chapter 24, track quality is deteriorating due to traffic, showing various faults. The development of the track quality is shown in Figure 113.

The Infrastructure Manager aims at a high quality track not only when the track is new (high initial quality), but also during its life. In order to take the right decisions for maintenance he must have

right standards for monitoring the track condition

proper track condition analysis tools

right track condition data’s (information) to be analysed, in order to understand the track behaviour.

processes to assure the proper working of the whole monitoring system.

Investments on the railway track refer to assets with very long life. Today many tracks are over 100 years old. Of course some track elements are replaced during maintenance actions over the years, but other track elements might remain the same - especially the substructure. In any case, a large amount of maintenance is necessary to ensure this long life.

Optimization of the track construction or the track components regarding technical and economic requirements is essential for railway companies to fit the market and to compete against other means of transport. LCC

67

and RAMS

68

technology are two acknowledged methods for assisting the

optimization process

regarding those requirements.

Railway RAMS is a major contributor to the

quality of service

provided of the Infrastructure Manager.

A system can be defined as an

“assembly of sub-systems and component connected together in an organised way, to achieve specified functionality”

. Functionality is assigned to sub-systems and components within a system. The behaviour and state of the system is changed if the sub-system or component functionality changes. A system responds to inputs to produce specified outputs, whilst interacting with an environment.

The system life cycle is an arrangement of phases, each containing tasks, covering the total life of a system from initial concept through to decommissioning and disposal (see Figure 156 in Chapter 36).

The life cycle provides a structure for planning, managing, controlling and monitoring all aspects of a system, including RAMS, as the system progresses through the phases, in order to

deliver the right product at the right price within the agreed timetable

.

Economical evaluations need to take into account all cost consequences of an investment, independent from the point of time and the place of the payment caused by the investment

75

.

Life cycle costing is the process of economic analysis to assess the total cost of acquisition and ownership of an asset.

The maintenance strategy consists usually of various

critical success factors

that are necessary to achieve the overall

goals for maintenance

.

Effective measurement of the condition of the track is necessary for the achievement of track maintenance goals. Figure 161 describes an approach to achieve track maintenance goals by analysing track condition data using RAMS and LCC (input for the LCC analysis see par. 36.4).

There are a number of conceptual models for the integration of RAMS and LCC in the design process. In this section a model is described to show how RAMS and LCC can be implemented in sectors such as the production industry.

The project in the following example is based on a project described in [111] that has been modified to adapt -as an example- to railway projects.

The terms Whole Life Cost (WLC) and Life Cycle Cost (LCC) have been used interchangeably - and their meanings have become confused.

WLC is a methodology for the systematic economic consideration of all whole life costs and benefits over a period of analysis, as defined in the agreed scope.

Track construction requires large investments.

The sole purpose of investing is a high initial quality. The sole purpose of maintenance is to assure that this initial quality leads to an extension of the service life of the track. Investment and maintenance should be viewed as elements of a strategy for the superstructure.

Traditionally, governments own public infrastructure such as railway, roads, communication networks, public buildings, and other public facilities. Usually maintenance of these infrastructures is done in-house. However, there is a growing trend towards outsourcing these maintenance activities to external agents.

Outsourcing has been engaged by industry as a useful tool to improve their efficiency. However, the main reason why organizations employed outsourcing was in the 1980’s less strategic, and more tactical.

According to a survey (1991), the biggest benefit that organizations expected by introducing outsourcing was a reduction of overhead and short-term costs [123]. Such a simple task as the cleaning of office buildings, distributing internal mail and so forth had been outsourced.

Outsourcing can bring a certain amount of benefit to the organization. Outsourcing also has advantages and disadvantages. Thus, careful consideration is required before making decisions about introducing outsourcing.

In some countries (United Kingdom, Netherlands) routine maintenance is fully contracted out. In the Netherlands, for example, this maintenance is contracted out to contractors by so-called “output process contracts”. In these contracts a precise description is given of what is wanted with respect to quality. Contractors are responsible to achieve this quality. The Dutch rail Infrastructure Manager does not tell the contractors how to carry out the maintenance, but evaluates the quality by several modern measuring instruments, and by monitoring and analysing disturbances. This means that in these countries the contractors are responsible for the diagnosis of routine maintenance [77].

After signing the contract with an appropriate external agent (contractor), the next concern is to monitor performance, since a certain amount of responsibility is transferred to the contractor.

According to a dictionary, the word “contract” is

a legal document that states and explains a formal agreement between two different people or groups, or the agreement itself

. Each prospective party, who is going to make a contract, has an expectation toward another party, and negotiates with each other on monetary and environmental conditions, and finally, if it is acceptable, reaches a formal agreement. A contract is a product of these rigorous processes[120].

Let’s make the hypothesis that the Infrastructure Manager decides to outsource its track maintenance to an external contractor. The next concern is what kind of contracting he should choose to ensure that the outsourcing is successful.

Well-managed contracts can bring significant benefits to an organization. Risk management is among the important issues in contract management. The following table presents some steps for risk management[120].

The parties involved in the development of the outsourcing scenarios are, as already discussed:

Owner of equipment: Infrastructure Manager (IM)

Service agent: Contractor

Total costs of service contract may include the cost of planned preventive maintenance and corrective maintenance in the form of minimal repairs and failure replacement, cost of inspections and condition monitoring, cost of risks, and penalties for failure to meet agreed safety, reliability and availability of requirements[119].

Data management when outsourcing certain important activities is crucial. If an Infrastructure Manager (IM) has contracted out the maintenance and renewal work to one or more contractors, the task of the Infrastructure Manager concerning the collection of infrastructure data will change. Apart from some visual spot checks of the track from time to time, the IM does not itself collect the infrastructure data needed. It has to rely on the data collected and presented by the contractors. The role of the IM turns into one of managing the data collection, instead of performing it itself.

The experience in Swedish Transport Administration “Trafikverket” could be traced back to 1988 when the Swedish Railways was vertically separated into two parts: the Swedish National Rail Administration, with responsibility for the infrastructure management; and the Swedish Railways with responsibility of running train services.

In the following, some lessons learned from ProRail (Netherlands) experience and advice for outsourcing are given [127]:

The infrastructure as the main production factor in the railway system’s value chain accounts for a significant part of the full system costs. Therefore it is very important for Infrastructure Managers to have good control of infrastructure management in general and of costs in particular to improve competitiveness.

The most important cost driver is the initial quality. For permanent way this means especially a high quality demand of subgrade. Subgrade quality dominates the behaviour of track. Therefore an excellent substructure quality is a precondition for any optimization.

“You can’t manage what you don’t measure”

. It is an old management adage that is accurate today. Unless you measure something you don’t know if it is getting better or worse. You can’t manage for improvement if you don’t measure to see what is getting better and what isn’t.

Numerous definitions of benchmarking have been developed. Benchmarking is defined as

“a process by which something is measured in relation to best practice”

. For Main

98

“benchmarking is the art of finding out, in a perfectly legal and above board way, how others do something better than you do - so that you can imitate - and improve upon - their techniques”

.

For an Infrastructure Managerit is of high importance to have a clear view on the state of its infrastructure.

To be able to manage the maintenance and renewal process efficiently and economically, an Infrastructure Managerhas to set up databases describing the infrastructure and its current state. The databases should provide enough up-todate information on the infrastructure in such a structured way that the Infrastructure Manager can efficiently use this information to develop the right policy for maintenance and renewal. In case the Infrastructure Manager outsources the M&R projects, the contractors will be responsible for the input of useful infrastructure data. The infrastructure manager’s role concerning the data gathering process will become more steering, controlling and facilitating.

In the following, we describe the infrastructure data that should be available in order to make good management possible. It will also elaborate on the data gathering and storage process, first in a situation where the Infrastructure Manageris gathering and storing infrastructure data himself and second in the situation that (a part of) the Maintenance & Renewal (M&R) activities are outsourced[79].

When rail vehicles run on a track, the wheels cause tangential and normal forces, as well as vibrations. This results in deterioration, influencing system performance and limiting life of components on both vehicle and track. In order to maintain the performance and safety of the system, the track has to be inspected, maintained or renewed. All these actions result in costs.

A method for estimating costs related to maintenance and renewal of the track is presented in this chapter.

Most of the tracks have been constructed many years before, but the demands put on the tracks today are different from the ones when the tracks were built. During the past decades there were major changes in rail. The maximum axle load increased significantly, as well as the train speed (Figure 179), the loco power and the train density. Today more trains are running on the track and the competition with other means of transportation becomes harder. At the same time there is also a tendency towards decreased time for maintenance and also decreased funds for maintenance.

The railway is a complex engineering system with long-life assets. Changes require an engineering-led vision of the railway, embodying both (Figure 180):

changes to the system using the best of current technology and

a prediction of the changes that may be brought out by new technology.