In many trains the bogie area is uncovered up to the height of the wheel. In order to minimise drag in high speed trains, the bogie areas may be covered with smooth and streamlined surfaces.

Technical details and design requirements

The greatest reduction in drag can be expected for bogie fairings fitted flush to the external contour of the train. However, this generally requires inside frame bogies. In the case of bogies with outboard journal frames, bellied bogie fairings have to be chosen. From an aerodynamic point of view, the latter need to be designed very carefully to avoid flow separation.

Fairings have to be designed in an optimised way both for aerodynamics and for cost-effective maintenance.

The fairing geometry has to respect a number of requirements which depend on the respective train design and infrastructure: For example for the ETR 500 the fairings had to respect the gauge limits and to avoid interference between bogie and car elements such as yaw dampers, doors, etc. In addition, openings on the fairings were necessary to allow, for instance, the view on brake indicators.

As a result, it is usually not possible to exploit the aerodynamic reduction potential up to 100 %. For newly designed stock, there are obviously less restrictions than for retrofitting measures.

Fields of application

• Main-line and high-speed trains
• There is a similar measure discussed for freight trains which is however mainly aimed at noise reduction and therefore not considered here.

Manufacturer:

Manufacturers of railway vehicles. The bogie fairings for the Italian ETR 500 were manufactured by AnsaldoBreda.

• Noise reduction
• Energy efficiency (Future high speed trains with increased speed will generate a strong rise in the energy costs of operations through increased air drag.)

Maintenance

For maintenance purposes an easy access to the bogies is required. Bogie fairings obviously make access more difficult, but this problem can be minimised by intelligent construction.