Page 41 - 360.revista de Alta Velocidad - Nº 5

Technological, economic and sociological factors on the maximum design speed of high speed trains

speed. Either the track-side objects like noise barriers or signal installation are placed at a
larger distance from the track or the objects are designed more sturdily to withstand the higher
loads.
In the range of 200 to 300 km/h the aeroacoustic emissions of a typical high-speed train are
in the same order as the wheel-rail sound. At higher speeds above 300 km/h the aeroacoustic
effects dominate [23]. The flow around structural elements like the parts of a pantograph cause
a dipole type sound emission whose intensity scales with U⁶ [24] [25]. This means a pantograph
at 600 km/h radiates about 64 times more acoustic power to its surrounding than at 300 km/h.
The measurements presented by Kurita [26] showed that a reasonable noise reduction can be
achieved by using aerodynamically optimized pantograph geometries, acoustically absorbing
surfaces, and so called noise insulation plates on the roof of the train (see also Yamada et
al. [27] and Ikeda et al. [28]). The insulation plates shield the acoustic emissions from the
pantograph in lateral direction. The experiments of Baldauf et al. [29] showed that by using an
actively controlled single-arm pantograph it is possible to reduce the pantograph noise about
10dB compared to the standard pantograph installed at the German ICE trains. Combining new
pantograph designs and noise insulation plates, it appears not unrealistic that the radiation
intensity of the pantograph noise at 600 km/h can be reduced to today’s standard level at
330 km/h. Thus the aeroacoustic emissions of pantographs do not constitute an insuperable
obstacle for train speeds above 400 km/h.

3.3 Signaling and Train Control

In an approximation the braking distance grows quadratic with the speed, which means that the
minimal braking distance increases from 2800m to estimated 11.2 km at 300km/h. Hence it is
state of the art, that drivers cannot control the train by trackside signaling at speeds above 160
km/h. Nevertheless all the elements required for a suitable train control and signaling system
are available today:
• Cab Signaling

• Safe and reliable radio connections
• Safe on-board Localization
• Train Integrity Supervision in multiple units

• Continuous control and supervision of speed
• Train separation by moving block
• Automatic Train Operation (ATO)

Most of the Elements are part of the European Rail Traffic Management System ERTMS and
proven in use. Only two of the required technologies are currently objective of ongoing research
activities: moving block and ATO. Therefore it can be stated that the signaling needs to be
adopted for very high speeds but it is not limiting the development.

4. Operational Aspects related to higher train speed

Travel time savings are only possible if the train uses high-speed lines (HSL) for a big part of the
journey. Therefore new tracks are necessary to increase the speed to over 320 km/h, which is
the current speed maximum in Europe.
Furthermore an efficient operation is only possible with lines exclusively used by high-speed
trains during the operation time of day. The higher the speed difference on mixed-traffic lines

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 39