5. Direct electro-pneumatic brake

When the first automatic control systems for metros appeared in the 1960s, the problem arose of the response times of compressed-air pneumatic braking: these response times soon proved incompatible with automatic control, mainly because of the time required to transmit braking and brake-release commands along the train, rather than the local response times for variations in force at the level of each vehicle or bogie in the train.

The answer soon came in the form of the use of power lines, as was already the case for traction control.

This gave rise to what is properly termed the electro-pneumatic brake, i.e. a brake whose train control uses electric train lines and whose local execution (force generation) uses pneumatic technology.

We'll see later that this term covers a wide spectrum of technologies, some of the...