initially, the ma 51 model trains, which had previously been used on line 13 until it joined line 14, circulated the tracks of line 10. these trains were first constructed with three cars on four chassis per train; two trains permanently connected to make six cars per train, having an equivalent capacity to five cars on the classic métro trains. because of the ineffectiveness of the ma 51 model, it was eventually completely replaced by the mf 67 model.