 After some difficult early days (involving a number of derailments), the locomotives later became part of the SNCF's 3-231.B class.The class was initially numbered 231-011 to 231-060 by the Chemin de fer de l'État and then 3-231.B.1 to 3-231.B.60 by the SNCF.The design of the 231s was based on two locomotives types