NEW LINES FOR SPEEDS OF 300 – 350 KM/H
1 –PRELIMINARY REMARKS
New railway infrastructure has been built for high speed traffic over a period
of more than forty years between the mid 1950s and the current decade. Hence
the criteria adopted for line design have changed in the course of time,
reflecting advances made in knowledge about the different aspects connected
with operation at higher speeds.
In particular, track geometry parameters adopted in projects for new
infrastructure for a given design speed allow for higher top speeds than the
speed at which the line is operated on commissioning, the latter being chosen
on the basis of technical, commercial and economic criteria.
Experience has shown that design engineers have sought to allow a certain
margin for higher speeds for the future. Because the service lives of
infrastructure and rolling stock are different, it is advisable to provide for this
margin which competition and current standardisation work may in fact
reduce.
Graph 1 shows the increase in maximum speeds in trials and in revenue
service over the last few decades.
km/h
INCREASE IN MAXIMUM SPEEDS
Graph 1
600
500
max speed in trials
400
300
200
max revenue speed
100
0
19501952 19541956195819601962 19641966196819701972 19741976 19781980198219841986 1988199019921994199619982000
Revenue service experience has been concentrated thus far in the 250 to 300
km/h speed range although, as mentioned above, some lines have been
approved for speeds as high as 320 km/h.
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Nonetheless, it has to be recognised that on the whole, economic
considerations (be they commercial or energy-related), as well as technical
(concerning rolling stock of permanent way installations) and environmental
protection considerations (line alignment, noise, etc.) have put a cap on high
speeds until now.
Yet, the picture can be expected to change in the future for some lines and for
certain types of high speed service. In Europe, the new Mediterranean TGV
line (some 60 kilometres of this line are to be operated at the speed of 320
km/h) and the Madrid – Barcelona line will be the first to evolve.
A working party was set up at the International Union of Railways in 1998 at
the request of GIF, the rail infrastructure manager in Spain, with the aim of
analysing the most critical aspects of high speed rail systems and to prepare a
preliminary draft of recommendations if possible.
The group quickly recognised the difficulty for a single group of experts of
addressing the full range of issues related both to permanent way and rolling
stock.
Furthermore, UIC had already carried out studies in certain specific fields to
resolve some of the problems falling within the scope of the group’s
investigations as well as work on the Technical Specifications for
Interoperability (TSI) and for various European standards on the
infrastructure, energy, maintenance, control command, rolling stock and
operations sub-systems.
Hence it was decided in a first stage to draw up a summary of the criteria
currently applied in various countries even though these may not yet have
acquired the status of standards.
More specific issues will now be addressed in a second stage and some of the
singular aspects or parameters analysed in greater depth with a view to
drawing up more precise recommendations.
The working party has focused on identifying the main problems involved in
raising speeds above 300 km/h, but without specifying any absolute
requirements.
2 – TRACK GEOMETRY PARAMETERS
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Line operation characteristics differ substantially from one country to another.
There are three types of lines from the standpoint of the type of traffic
operated :
Type 1 : Lines dedicated to high speed traffic. This is the practice in France
and Belgium and in the future, the same approach will be adopted for certain
other lines in Germany (Cologne - Frankfurt)
Type 2 : Lines used for high speed passenger traffic as well as for
conventional trains at lower speeds. This is the case in Spain as well as for
future lines in Belgium.
Type 3 : Mixed traffic lines used for both passenger trains (high speed and
conventional) and freight trains as in Italy and Germany as well as for future
lines in Spain, France and Great Britain.
The initial consideration of the type of traffic to be operated on a line is of
prime importance because it has an immediate and fundamental bearing on
line layout, maximum permissible axle loads, operating conditions and
equipment and on maintenance.
The combination of freight traffic and trains operated at speeds of over 300
km/h may pose capacity problems, but can also create severe track geometry
constraints because of restrictions on excess cant. For all of these reasons,
traffic at speeds above 300 km/h should be confined to type 1 and 2 lines as a
rule.
This initial consideration has a decisive impact on line alignment parameters
such as the maximum gradient for which there is a very wide range of 12.5 to
40 ‰, clearly highlighting the fact that it is impossible to set a recommended
value because the traffic and terrain of the regions crossed by a new line may
be the prime factors guiding decisions.
Nonetheless, it should be borne in mind that the draft TSI for infrastructure
specifies a maximum gradient of 35 ‰ over a continuous 6 km stretch of
track, added to which the slope of the mean sliding profile over 10 km must be
less than or equal to 25 ‰.
Logically the higher the design speed for a line, the larger the curve radius
should be. At all events, once the maximum speed criterion has been set for a
line, the key parameter for determining the other geometric characteristics of
the line is cant deficiency.
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Table 1 summarises the main track geometry characteristics for different
railways based on experience to date.
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FRANCE
PARAMETER
Type of traffic
Maximum axle load for the
max. line speed, HS trains (t)
Maximum axle load for
locomotives (t)
Maximum axle load for wagons
(t)
Minimum curve radius for
maximum speed (m)
Maximum cant (mm)
Maximum gradient (mm/m)
Cant deficiency at design
speed (Cd, mm)
300 KM/H
LINES
GERMANY
300 KM/H
350 KM/H
LINES
LINES
Nuremberg Ingolstadt
PASSENGER PASSENGER
ITALY
300 KM/H
LINES
Cologne Frankfurt
350 KM/H
LINES
Study
assumption
PASSENGER /
PASSENGER
FREIGHT
PASSENGER
300 KM/H
LINES
SPAIN
350 KM/H
LINES
Study
assumption
300 KM/H
LINES
BELGIUM
350 KM/H
LINES
300 KM/H
LINES
PASSENGER / PASSENGER /
PASSENGER PASSENGER PASSENGER
FREIGHT
FREIGHT
TSI
(Draft)
350 KM/H
LINES
Study
assumption
PASSENGER
17
17
17
17
< 16
17
17
17
18
17
17
-
-
20
-
-
22,5
22,5
20
-
22,5
-
-
-
22,5
-
-
22,5
22,5
-
-
22,5
-
4 000
3 350
5 120
5 450
7 000
4 000
6 500
4 800
160
170
170
105
130
150
150
150
20
40
40
12 (6)
12 (6)
12,5
25
15 (21)
105
130
ballasted
track
150
ballastless
track
112
90
75
100
65
100
180
6 250
exc.(5 556)
180
35
35
4 000
85
65 (85)
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Defined by
Cd
200
35 (long
< 6 km)
80
3 - CHARACTERISTICS OF THE TRACK CROSS SECTION AND OF
THE INFRASTRUCTURE
The most significant parameters to be considered in respect of higher speeds
are the distance between track centres, tunnel cross sections and the location
of access ways for maintenance staff.
DISTANCE BETWEEN TRACK CENTRES
The TSI specify a minimum value of 4.50 metres for the distance between
track centres (for speeds above 300 km/h). Some railways have adopted
different values, in some instances without explaining the reason for this.
The economic implications may be substantial if the cross section is enlarged
(either to widen the distance between track centres or for the other parts of the
lateral profile)
Some of the studies carried out for the international Figueres - Perpignan
section of the Barcelona - Perpignan new line show that an increase in the
distance between track centrelines from 4.5 m to 4.8 m adds a further 1 % to
civil engineering costs.
The track cross section must be considered in the light of local features such as
drainage, access ways, earth walls replacing noise abatement walls, etc.
TUNNELS
In the section on infrastructure parameters in the Technical Specifications for
Interoperability, it is significant to note that the tunnel cross section must
comply with the criterion for maximum permissible pressure variations. It is
stated in this respect that tunnels must be designed so that the maximum
pressure variation along an interoperable train shall not be more than 10 kPa
during the time taken for the train to pass through the tunnel at the maximum
speed permitted.
This limit has been set as a precaution in the event of failure of the pressuresealed system and the values adopted have been set from the standpoint of
passenger health and not comfort.
On mixed traffic lines, freight train operation in double-track tunnels poses
two problems : aerodynamics and safety in the event of an accident. For this
reason, high speed trains must be run at lower speeds in tunnels or should not
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be operated in combination with freight trains, timing the latter in separate
slots.
Tunnel lining has a positive impact on aerodynamic effects.
Furthermore, the subject of traffic safety inside tunnels should be addressed
from the standpoint of infrastructure and in terms of the measures taken to
handle emergencies.
In this respect, one of the issues to be explored is the permissible length of
tunnel for each type of track, i.e. the maximum length of double-track tunnels,
crossovers inside tunnels to allow for two-way working, emergency exits
(maximum distance between exits, configuration, facilities, shelters, etc.) and
requirements for mixed passenger and freight traffic.
TRACK GANG SAFETY
One extremely important point for track gang safety is the distance between
the edge of access ways and the outside edge of the rail. Once again there are a
wide variety of criteria to define this parameter which ranges between 2.15
and 3.00 meters.
The TSI specify that trainsets at 250 km/h shall not cause dangerous
slipstream effects on persons at a distance of 2 metres.
For higher speeds, each railway will have to consider whether additional
precautions need to be taken, such as increased clearances, protective screens,
etc.
BRIDGES
Dynamic effects.
Disturbances have been identified in ballast beds causing instability in the
track and deterioration in track geometry (creating a certain risk for traffic).
An in-depth study of this occurrence has shown that the instability is caused
by vertical acceleration in bridge decks which can be as high as 0.7 g and even
0.8 g. The vertical acceleration is caused by the passage of trains at certain
speeds and not necessarily at top speed.
This level of vertical acceleration triggers ballast liquefaction causing the
ballast to become fluid and consequently reducing track strength.
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Furthermore, the regular and repeated load distribution of high speed trainset
axles in certain speed ranges may give rise to resonance in bridge decks and
amplify deflection and vertical acceleration substantially.
Consequently, it is vital to check the behaviour of railway structures on very
high speed lines at the design stage.
In particular, Eurocode trains must be used to ascertain that vertical
acceleration on bridge decks does not exceed the values of 0.35 g (ballasted
track) and 0.5 g (ballastless track), and that there is always a safety coefficient
of 2 in the frequency band below 20 Hz.
Loading tests.
Structural and loading tests must be carried out to ensure that the dynamic
parameters (stiffness, natural frequency, damping, etc.) of engineering
structures are identical to the design values.
Transition between earth structures and engineering structures
Transitions between engineering structures and earth structures (bridges,
viaducts and tunnels). These are sensitive parts of infrastructure which can
suffer from two types of problems : rheological problems and change in
stiffness.
Rheological problems are normally associated with differential settlement
between two types of structures and longitudinal levelling. They give rise to
additional costs for maintenance, mainly in the initial years of operation of a
line; subsequently, the problem is less marked.
Change in vertical stiffness is directly influenced by speed and causes higher
Q forces at the wheel–rail interface, track and ballast deterioration and also
higher maintenance costs. Vertical stiffness also has an impact on comfort.
The problem also occurs on ballastless track.
There are several solutions to this problem based particularly on use of
selected granular materials and / or sub-grade transition structures with
different geometry, consistency and dimensions depending on circumstances,
but generally very costly.
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The same type of sub-grade transition structure is used for both 300 km/h and
350km/h lines, but given the large number of engineering structures on new
high speed lines, it would be advisable to study the solutions and dimensions
needed for these transition elements.
Expansion joints.
Insofar as possible, long viaducts should be designed bearing in mind the need
to reduce (or eliminate) the number of expansion joints which are frequently
too long and also pose considerable maintenance problems.
4 - ENVIRONMENT
The environmental aspect most influenced by higher speeds is noise; the
characteristics of noise change depending on speed and when speed increases,
the prevailing noise is that of the train engine up to the speed of 120 km/h,
followed by running noise at 200 km/h, and then by the noise of pantographs
and aerodynamic noise above 250 / 300 km/h.
As speed increases, the level of noise emission and the nature of noise changes
also, rendering noise abatement walls less effective.
As a rule, it is legitimate to assume that the higher the speed, the more noise
problems there will be. Consequently, provision must be made for protective
measures (noise abatement walls, earth walls, etc.), as well as for changes in
line layout or the construction of artificial tunnels or covered cuttings,
maintenance measures (grinding) and of course measures on rolling stock.
Graph 2 shows the different criteria and values obtained between 200 and 300
km/h.
Graph 2
Noise Level [dB(A)]
Graph 2
105
TRANSRAPID
95
ICE
85
STI
IC - DB AG
75
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65
100
200
300
400
500
Speed (km/h)
5 – TRACK EQUIPMENT PARAMETERS
RAILS
There is general agreement among the railways that the same types of rail can
be used irrespective of the speeds practised on a line. Hence the type of rail
recommended for the speed of 300 km/h as well as for 350 km/h is the
standard 60E1 type rail (UIC 60). Specialists are also unanimous about the
grade of steel (900 A).
On the whole, the quality of rails is not affected by raising speeds above 300
km/h if top quality rails are used. However, special attention should be given
to acceptance, laying, welding, superficial flaws, etc.
Some railways consider that the elementary sections of rail used to
manufacture CWR should not be 36 metres long systematically so that trains
will not pass over evenly-spaced welds possibly triggering critical
wavelengths.
The TSI recommend a rail cant of 1:20 for speeds above 280 km/h. Similarly
they specify the track gauge, rail cant and wheel profile values for the lowest
conicity possible at speeds above 280 km/h (without any distinction being
made between 300, 350 km/h, etc.).
As a rule, the higher the speed, the lower the equivalent conicity should be.
The wear profile should be studied from the standpoint of economic efficiency
and compliance with the theoretical equivalent conicity.
SLEEPERS
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Normally speaking, the various railways do not plan to make any changes in
the mass per kilogram of sleepers to prepare for operation at speeds of 300
km/h and above.
The bearing surface of sleepers is a key factor for distributing vertical forces
on the ballast. If the forces exerted on rails increase with the higher speeds and
are transmitted to sleepers through baseplates and to the ballast, it would be
highly advisable to assess dynamic forces and other additional forces (due to
braking in particular).
BASEPLATES, FASTENING SYSTEMS AND TRACK STIFFNESS
Track stiffness must be contained by means of the appropriate baseplates
placed beneath rails in order to reduce the vertical dynamic wheel-rail forces
exerted.
Baseplates are generally made of rubber or elastomer and one of their main
characteristics is vertical elasticity. They are particularly important on bridges,
in tunnels and on slab track.
An analysis of the values used in the different countries reveals large
differences in both baseplate thickness and vertical stiffness.
Graph 3 provides an idea of the optimisation of vertical track stiffness (as a
whole) depending on the different parameters involved, the vertical dynamic
stresses of non-suspended masses and the energy dissipated by track
distortion. Conversely, excessively high baseplate stiffness can have an
adverse impact on concrete sleepers.
Graph 3
Energy dissipated in the track
Vertical dynamic stresses
exerted by non-suspended
masses
Deterioration in longitudinal leve
Optimal stiffness
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Given the importance of vertical track stiffness in track-vehicle dynamics, this
aspect should be investigated in depth to ascertain the optimum value for each
variable.
The trend today is to design track for an overall stiffness of about 100 kN/mm.
At all events, track stiffness values should be uniform along the entire length
of a line.
A reference value should be set for both vertical track stiffness and for track
damping in order to assess generally whether train traffic can be operated at
the speed of 300 km/h and above on a line without giving rise to unduly heavy
maintenance costs.
TRACK LAYING
On the whole, high speed lines in Europe consist of ballasted track in most
instances. Nonetheless, DB AG also has ballastless track on which trains are
operated at speeds above 200 km/h. This type of track is used in France also
on underground sections of line operated at 220 km/h.
BALLAST
There are no significant differences from one country to another regarding the
size of the smallest particles used for the ballast on high speed lines. Any
differences are often due to the national standards applied.
A European standard is currently under preparation on : “ Aggregates for
railway ballast” the draft of which was ready in April 2001 for submission to a
vote. The draft standard does not specify requirements for high speed lines.
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Special attention is given to the presence of fines in the ballast. In some
instances the ballast needs to be washed (sometimes twice).
Interim storage should be avoided because it fosters ballast segregation (the
smallest particles tend to sink to the bottom of the ballast materials).
Furthermore, the mechanical characteristics of the ballast and in particular
hardness must be taken into account (Los Angeles coefficient, Micro Deval
coefficient, overall hardness coefficient, etc.), resilience, grain size, the
proportion of fines, etc.
Today’s high quality ballast can be used without posing any particular
problems for 350 km/h lines, as requirements do not in fact vary to any large
degree between 300 and 350 km/h.
Ballast behaviour under vibrations (fluidification) at different speeds should
also be analysed and at the same time it should be ascertained whether
vibration insulation mats are needed or not (generally this type of material is
not used on high speed lines except in specific instances).
Important aspects such as ballast attrition or attrition of other particles on the
track, slipstream effects or ballast scatter and the definition of a standard
ballast layer profile (which is important among other things to combat
slipstream effects) also require attention when operating speeds are raised.
Mesh grating should be installed in some locations to prevent ballast
projection outwards.
Blocks of ice formed on vehicle undercarriages cause ballast projections
which in turn damage rails. Special care should be taken when trains are
operated at speeds above 300 km/h.
BALLASTLESS TRACK
Several railways (DB AG, FS, SNCF, JR) have built ballastless track. In
Germany, in particular, DB AG decided to build ballastless sections of high
speed line (or lines designed for speed above 200 km/h) except in areas where
trains should run at lower speeds, for example in the vicinity of stations.
On the whole, construction costs for ballastless track are much higher than for
ballasted track, but experience has shown that maintenance costs are about 1/5
lower, expecially in tunnels because the track geometry deteriorates more
slowly.
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Nonetheless, it is too early to conclude that the total life cycle cost of
ballastless track will be much lower than for conventional ballasted track.
Some of the decision factors to be considered in this area are :
-
the cost of construction and maintenance of points and crossings
(including financial charges)
line availability (and consequently, the possibility of increasing
capacity) since less time will be required for maintenance
-
greater lateral track strength
-
the drawbacks (the eventuality of construction flaws, more noise, etc.)
and the impact on total life cycle costs
-
the cost of repairs for maintenance or in the event of derailment
-
the consequences of a derailment
OTHER TRACK-RELATED ASPECTS
Other types of track tested to variable degrees (track laid on asphalt, track with
special fastenings, ladder track, Riessberger track, etc.) are not used for high
speed lines for the moment.
Points and crossings, bridge bearings, transition structures, etc have not been
addressed in this study for the time being.
6-
ELECTRIFICATION, SIGNALLING, TELECOMMUNICATIONS
AND OTHER LINE EQUIPMENT
These aspects will be addressed in greater depth in a second stage of the study.
A few preliminary considerations have been noted nonetheless.
With the exception of Germany where the track is electrified to 15 kV,
16 2/3 Hz, the other countries mentioned in the report have all adopted the 2 x
25 kV, 50 Hz system. These types of electrification systems are still suitable
for services operated at 350 km/h.
The catenary tension required depends on train speeds and ranges from 15 kN
at 250 km/h, to 20 kN at 300 km/h and 30 kN at 350 km/h. New alloys have
made it possible to increase catenary tension.
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Contact wire height for the different countries falls within the values specified
in the draft Technical Specifications for Interoperability (TSI), i.e. 5.08 or 5.30
m.
To operate at higher speeds, more power is needed and therefore in some
instances, it will be necessary to reduce the intervals between sub-stations.
Where signalling is concerned, as a rule, ERTMS can cater to speeds of up to
500 km/h.
7 – OPERATING CONDITIONS
WEATHER CONDITIONS
On the whole (and apart from the impact on overhead lines, for which catenary
tension must be raised in order to increase resistance to sidewinds), train
sensitivity to sidewinds (from the standpoint of stability) increases with speed.
Generally, speed restrictions are required when the sidewind velocity exceeds
certain values (on some railways, SNCB for example, the permissible limit of
wind velocity applies to all directions). If wind velocity exceeds certain
values, traffic may have to be stopped.
In some instances, windscreens may obviate the need for speed restrictions
and eliminate the risk of high speed trainsets overturning.
At very low temperatures, blocks of ice may form underneath vehicles and
falling ice may cause ballast projections (see section on ballast).
MAINTENANCE
Depending on the distance between track centres and the track gang danger
zone circumscribed (which varies from one country to another), the presence
of track gangs for inspection or maintenance work may mean that speed will
have to be reduced to below 350 km/h on tracks remaining in service.
As far as technical aspects are concerned and from a general standpoint, there
should be a requirement at speeds of 350 km/h for systems able to detect and
correct very long wavelength faults.
Inspections should be carried out to ensure compliance with maintenance
standards (tolerances, quality of track geometry, wear, rail grinding - which
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should diminish the need for tamping as a rule - welding, grinding of welds,
traces on rails, etc.).
8 – CONCLUSIONS AND RECOMMENDATIONS
Drafting of recommendations for the planning and operation of a line designed
for speeds ranging from 300 to 350 km/h involves work lying well outside the
scope of a single working party.
The members of the group hold the view that with experience acquired in
railways in the field of high speed operation, the transition from 300 to 350
km/h can be achieved with current technology.
Nonetheless, this report has identified certain subjects that are influenced by
speed and others where clearly the decision to opt for the speed of 350 km/h
rather than 300 km/h has no impact on the criteria adopted insofar as no new
threshold has been identified.
It would be advisable to set up specific working parties to address some of the
topics identified and this work could be coordinated by the UIC High Speed
Division.
However, it is also clear that a substantial amount of time would be required to
prepare recommendations on certain points.
One of the priorities has been to draw up recommendations concerning those
elements that cannot be changed after a line has been built (track geometry, for
example) or where it would be very costly to make changes (this would be the
case for general civil engineering structures, tunnels and bridges).
Aspects connected with high speed line maintenance (and concomitant track
quality) deserve particular attention. A study on definition of maintenance
policy is still needed even though the added cost of maintenance for a high
speed line is not substantial.
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