Page 227 - 360.revista de Alta Velocidad - Nº 5

New design concepts for High-speed lines and the limits of the ballasted track

implementation of High-speed networks has been accelerated around a multitude of
countries throughout the world, generating a greater technical demand in the design of
the new lines and searching for new challenges that allow improving the existing service,
as shown in Campos et al. (2009).

In the case of the United Kingdom, this fact has clearly been reflected in the design
requirements established for the development of the HS2 project, which will provide
a Highspeed line connection among the cities of London, the West Midlands, Leeds and
Manchester, as explained by Greening (2012). These requirements set the future maximum
design speed at 400 km/h, as shown in Cornet et al. (2017), and 120 years of infrastructure
design service life. Therefore, the planned railway superstructure will be of slab track type
due to the important condition of the maximum design speed of the project.
On the other hand, in the case of Saudi Arabia, with the project of the Haramain High-
speed Line, there have been important problems such as the fight against the desert sand,
as shown in Sesma et al. (2012), and resistance to the extreme temperatures, as explained
by Durand et al. (2012). The line has been designed for a top speed of 320 km/h, with
758.6 km of ballasted track and 128.88 km of slab track. This decision regarding the track
typology is completely reasonable because of speed and country factor. According to the
data shown above the design speed of this project is in the range in which there is a mixed
use of track typologies and, on the other hand, Spain, which is one of the countries above
defined as main user of ballasted track in its High-speed lines, is the designer of the railway
superstructure.

In the case of Sweden, the East Link project, called Ostlanken in Swedish, is being developed
for a speed of 320 km/h, and it is expected that a slab track type will be implemented, as
per Trafikverket (2016, January). This decision is taking into account the two main factors
again. In first place, the design speed is in the range of using slab track as shown figure 2
and the companies which are designing most of the track sections are from Germany, which
is one of the countries above defined as user of slab track systems in its High-speed lines.
Finally, in the case of the United States, the High-speed line of California is still under
development and has been designed to reach top speeds of 350 km/h in the section
between San Jose and Los Angeles. The technical specifications leave open the door to the
application of slab track or ballasted track, although the latest reports of cost estimation
suggest that it will be used almost exclusively the ballasted track, reserving the slab track
only for sections of viaduct or tunnel.

4. Conclusions

Throughout the article a historical journey has been made on the different types of railway
superstructure installed since the appearance of the first High-speed line and have been
described two of the main factors that influence it: the maximum speed and the tradition
of design of the installer.
As it has been observed in the previous sections, in general, the typology of slab track is
experiencing a greater implementation in the High-speed lines that are being constructed at
the moment. This fact is mainly based on that the designs are being made for speeds higher
than the current ones and trying to reach the limit of 400 km/h. However, this trend has
important exceptions, such as the Haramain line or the California High-speed line that has
installed ballasted tracks, reserving the slab track only for those sections where it is specifically
needed. In the case of California, only in the areas of greater seismicity and in the sections
of tunnel or viaduct, and in the case of the project of Haramain for those section that need a
greater protection against the attack of the desert sand.

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 225