Technical development

The Gröna Tåget programme has covered a great many important issues concerning technical development, in particular the following aspects:

• Energy use
• Noise emissions, both external and internal
• Track-friendly bogies and suspension
• Carbody tilt
• Requirements for winter operation
• Aerodynamics, in particular air drag and stability in cross winds
• Electric propulsion – new motor and pantograph technology
• Safety and driver’s environment
• Standards for European and Scandinavian countries

Energy use

Thanks  to low air drag, eco-driving and a high amount of energy regeneration with electric braking, energy use per passenger-km is estimated to be low, i.e. 25-35% lower compared to current high-speed trains (X 2000 or SJ 2000) in Sweden. This is in spite of higher speed. The good space utilisation on board the Gröna Tåget and high-efficiency permanent magnet motor drive will also contribute.


External noise emissions from the train are not expected to be higher than for current trains (both high-speed and freight trains) at lower speeds. This is due to thorough noise abatement with damped wheels, bogie skirts and careful aerodynamic design. Measures that could be taken in confined sensitive areas (low track-close barriers and tuned damped rails) have also been tested. A thorough analysis of noise transfer paths for internal noise has been made.

Track-friendly bogies and suspension

Research, development and testing have been carried out in order to achieve running gear with modest impact on track, despite higher speeds than current trains. This is achieved by means of a newly developed radial self-steering bogie (RSS), which runs stably at high speeds and produces low wear to wheels and track in frequent curves on existing lines. An active radial steering bogie (ARS) has also been developed and type-tested.

Further, a system for active lateral suspension (ALS) is developed. A system for active vertical suspension (AVS) has also been conceptually developed. The two systems will guarantee a smooth ride also on non-perfect track, deteriorated by heavy freight trains and frost upheaval.  The RSS bogie, also equipped with ALS, has been type-tested and subjected to endurance testing for about 700,000 km in commercial service during 2009-2012, including two harsh winter periods. The AVS system shows very promising performance in simulations but remains to be tested.

A special study has been made of expected track deterioration, which showed that a modest axle load is important (max 15 tonnes at service load) as are radial steering bogies.

Carbody tilt

The existing curvy lines in Sweden and Norway will call for increased speed in frequent curves, in order to attain competitive and attractive travelling times. This requires both carbody tilt and track-friendly bogies.
The carbody tilt control has been further developed in order to attain optimum tilt and passenger comfort, depending on the actual curve geometry, train speed and passenger perception. The new tilt control system uses an on-board database for curve geometry of the track, and also a positioning system based on GPS. The new system is expected to improve passenger comfort and reduce the tendency for motion sickness, according to tests with human subjects on board a test train.

Requirements for winter operation

High-speed train operation in the Nordic winter climate is a challenge. Heavy snowfalls and temperatures as low as 30-40°C below freezing are normal and to be expected. These conditions may prevail for several weeks and even months. A standard European train is hardly suitable for these operating conditions.

Tests have been made of various technical solutions for reliable winter operation. Experience of necessary measures to be taken for reliable winter operation has also been gathered and documented. Hundreds or thousands of different details will be influenced.


High-speed trains should have as low aerodynamic drag as possible, while still respecting the requirements for low or modest turn-over forces caused by strong cross-winds. Requirements concerning slipstream speed outside the trains must also be considered. New prediction methods have been developed, as has a system for aerodynamic optimisation of the outer shape of the train. Through systematic optimization the air drag can be reduced considerably.

Electric propulsion – new motor and pantograph technology

New high-performance and efficient traction motors with permanent magnets (PM) in the rotors have been developed. The advantage is an improved power-to-mass ratio, i.e. the motor will be lighter and/or deliver higher output at the same exterior motor size. Another advantage is that PM motors may have about half the losses compared to the usual induction motors. This will have two effects: (1) energy use will be reduced and (2) simpler cooling may be used.

A new pantograph, suitable for high-speed operation on older existing catenary systems, has been developed. Its performance has been tested and shown to be superior. This is particularly important at multiple operation with up to three active pantographs in the same high-speed train.

Safety and driver’s environment

Studies have been made of the design of future driver’s cabs on high-speed trains with regard to information and safety systems. VTI has also developed a train simulator that can be used for research and education.

Train features for derailment worthiness, i.e. to ensure that the train remains above the track after a derailment, has been analysed and proposed. Other aspects are the train’s interior and luggage storage on board, which requires a design which takes internal safety in the event of an accident into consideration.

Standards for European and Scandinavian countries

A compilation of requirements according to the European standard (EN and TSI) has been made. Special requirements for Nordic conditions are also described.