A method for transforming between a long vehicle combination and a platoon on the move, wherein the long vehicle combination comprises a plurality of vehicles (14a-c) mechanically coupled together one after the other, which method comprises the steps of: detecting that the long vehicle combination is approaching a first road section ahead, by means of a navigation system or by means of wireless vehicle-to-infrastructure (V2I) communication, which first road section stipulates decoupling the vehicles (14a-c) of the long vehicle combination to form the platoon; automatically decoupling the vehicles (14a-c) from each other while the vehicles (14a-c) are in motion to form the platoon before reaching the first road section; the platoon driving through the first road section; detecting a second road section, by means of a navigation system or by means of wireless vehicle-to-infrastructure (V2I) communication, which stipulates coupling together the vehicles (14a-c) of the platoon to form the long vehicle combination; a vehicle (14a-b) in the platoon immediately ahead of a following vehicle (14b-c) of said the platoon sending information to the following vehicle (14b-c) via wireless vehicle-to-vehicle communication, which information indicates the position and speed of a rear automatic coupling device of the vehicle (14a-b) immediately ahead; based at least on the position and speed indicated in the sent information, autonomously driving the following vehicle (14b-c) so that the rear automatic coupling device of the vehicle (14a-b) immediately ahead of the following vehicle (14b-c) gets within an operational range of a front coupling element of the following vehicle (14b-c); while in motion and when the rear automatic coupling device is within the operational range, the following vehicle (14b-c) automatically adjusting a front coupling device including said front coupling element so that the position of the front coupling element matches the position of the rear automatic coupling device as indicated in the sent information; and automatically coupling together the following vehicle (14b-c) and the vehicle (14a-b) immediately ahead while the vehicles (14a-c) are in motion to form at least a part of the long vehicle combination, wherein each vehicle (14a-b) immediately ahead is adapted to estimate the position of its rear automatic coupling device based on the heading of the vehicle (14a-b) immediately ahead, the position of a part of the vehicle (14a-b) immediately ahead as determined by a navigation system of the vehicle immediately ahead, a vehicle model representing the vehicle (14a-b) immediately ahead, the height of the rear automatic coupling device, and in case the vehicle (14a-b) immediately ahead is an articulated vehicle, at least one articulation angle of the vehicle immediately ahead as detected by at least one articulation angle detection means on the vehicle immediately ahead. detecting that the long vehicle combination is approaching a first road section ahead, by means of a navigation system or by means of wireless vehicle-to-infrastructure (V2I) communication, which first road section stipulates decoupling the vehicles (14a-c) of the long vehicle combination to form the platoon; automatically decoupling the vehicles (14a-c) from each other while the vehicles (14a-c) are in motion to form the platoon before reaching the first road section; the platoon driving through the first road section; detecting a second road section, by means of a navigation system or by means of wireless vehicle-to-infrastructure (V2I) communication, which stipulates coupling together the vehicles (14a-c) of the platoon to form the long vehicle combination; a vehicle (14a-b) in the platoon immediately ahead of a following vehicle (14b-c) of said the platoon sending information to the following vehicle (14b-c) via wireless vehicle-to-vehicle communication, which information indicates the position and speed of a rear automatic coupling device of the vehicle (14a-b) immediately ahead; based at least on the position and speed indicated in the sent information, autonomously driving the following vehicle (14b-c) so that the rear automatic coupling device of the vehicle (14a-b) immediately ahead of the following vehicle (14b-c) gets within an operational range of a front coupling element of the following vehicle (14b-c); while in motion and when the rear automatic coupling device is within the operational range, the following vehicle (14b-c) automatically adjusting a front coupling device including said front coupling element so that the position of the front coupling element matches the position of the rear automatic coupling device as indicated in the sent information; and automatically coupling together the following vehicle (14b-c) and the vehicle (14a-b) immediately ahead while the vehicles (14a-c) are in motion to form at least a part of the long vehicle combination, wherein each vehicle (14a-b) immediately ahead is adapted to estimate the position of its rear automatic coupling device based on the heading of the vehicle (14a-b) immediately ahead, the position of a part of the vehicle (14a-b) immediately ahead as determined by a navigation system of the vehicle immediately ahead, a vehicle model representing the vehicle (14a-b) immediately ahead, the height of the rear automatic coupling device, and in case the vehicle (14a-b) immediately ahead is an articulated vehicle, at least one articulation angle of the vehicle immediately ahead as detected by at least one articulation angle detection means on the vehicle immediately ahead.