Original carriage (box car) of a holocaust train displayed at Auschwitz II (Birkenau)

A typical holocaust train that brought people to the death camps from different parts of Europe consisted of 50 box cars each with a carrying capacity of 50 people, i.e. 2,500 people per trainset. However, in order to speed up the final solution, the Nazis kept to a maximum of 55 freight cars on average, loaded from 150% to 200% capacity. During the mass deportation of Jews from the Warsaw Ghetto to Treblinka in 1942 trains carried even up to 7,000 per train! Between 1941 and December 1944, an estimated 4,000,000 prisoners mainly Jews have been transported to the death camps through Holocaust trains. A more detailed general article on the subject is here in Wikipedia.