The Bilbao underground train units (U.T. 500 & U.T. 550) are equipped with the latest technological systems existing in the area of railway transportation.
All the carriages are motor carriages, which makes their technical performance highly effective, especially as far as power, acceleration and braking are concerned. Each motor carriage is autonomous.
The four carriages which make up the train unit are joined, with no doors or separation of any kind. This way a single space is achieved, which provides greater mobility for travellers inside the train, better distribution and more comfort. The body of the carriages is a self-supporting structure built of welded stainless steel.
The UT-500 and UT-550 train units have the same appearance, but the latter includes some improvements such as the installation of a new air-conditioning system that can be controlled from the driver's cab, the carriages have better soundproofing and there are more handgrips.
Each motor carriage is equipped with heating-cooling equipment. The equipment has two independent cooling systems.
Each train unit has two motor-compressor units which provide compressed air at 10 Kg/cm 2, guaranteeing an air flow of 1,450 litres/minute.
A static converter produces the electric power necessary to feed all the auxiliary service power. There is also a battery system.
