The advent of modern power electronics and AC asynchronous traction motors has considerably reduced the volume of traction equipment. This (along with other technological developments) has facilitated the development of trains with decentralized traction, so-called electric multiple units (EMUs). A similar development has taken place in diesel traction.

In today’s railways, multiple units have replaced loco-hauled trains to a large extent in many segments, especially local and regional service. On high-speed lines the locomotive concept is still widely in use, although the Shinkansen and the ICE3 show that MUs are becoming an interesting option for high-speed service as well.

Figure 1: Technical data of high speed trains with distributed vs. centralized traction

Source: Hagiwara, Fukushima 2001