A method of conserving operating data of a vehicle, the method including the steps of collecting the operating data and recording it progressively on board the vehicle, detecting an event, as from a detection, transmitting to at least one external receiver firstly at least some of the data that is being collected and as it is being collected, and secondly at least some of the stored data in a chronological order that is the reverse of the order in which it was recorded, and recording the data received by said external receiver. A conservation system for implementing the method is also provided.