 However, it soon became apparent that replacing 6-car units with 4-car ones would lead to overcrowding, which caused IÉ to subsequently alter the proposal into sets of 3, 4 and 5-car lengths.The 20 cars taken off the original 6-car sets 22031–45 and inserted in the original 3-car sets 22011–30 got additional numbers 22811–30 but also kept the original number 22531–540,641,741,642,742,643,743,644,744,645,745.There have been attempts to improve the fuel economy of the 22000 Class.