The front door (1) articulates by means of upper hinges (2), assisted by dampers (3) connected to the internal structure (4) of the front door (1). It includes a lower portion (5) articulated by the lower hinge (6) to the structure of the vehicle (VP). The lower portion of the door (5) projects outwards when the front door (1) is opened through the action of cables (15) and pulleys (16). A retractable staircase (7) extends; when retracted, it folds under the floor of the vehicle (8). The front door (1) is activated internally by the passengers using a lever (9) that turns a rod (10), moving shafts (11) that release the locking mechanism. An electromagnetic safety key, making it possible to open the front door (1) if the vehicle breaks down.