Complex sentence: To save cost and weight, each carriage has only four bogies: the middle car part has two bogies; the end parts consist of one bogie each and are connected to the central portion via a so-called semi-trailer-direction.
Split into simpler sentences: To save cost and weight, each carriage has only four bogies. The end parts consist of one bogie each and are connected to the central portion via a semi-trailer-direction.