Method for warning of failure to observe a safety distance, using a warning system, to be provided on a first vehicle, the warning system comprising: - a device for measuring, where applicable, a clear distance at the rear of said first vehicle, between the first vehicle and a second vehicle that is following same; - a display disposed at the rear of the said first vehicle, for displaying a message as a function of the said distance, so that it is visible from the second vehicle follower, where applicable; - means for calculating a safety distance DS at least as a function of the speed of said first vehicle; - means (20, 9, 11, 12) for characterising a lane change of the first vehicle and for the system to analyse whether the first vehicle is stabilised in a traffic lane; - a device for recording an identity of the second vehicle follower and memorising a history of the distances as long as the second vehicle follower remains in a safety zone or at distance less than the safety distance DS, the display being, preferably, configured to display the identity; - a device for transmitting said identity to a remote server; the method comprising, after an initialisation phase, a phase of analysing the situation of the first vehicle consisting firstly in performing, in parallel: - an analysis of lane change to check that the first vehicle is stabilised on a traffic lane; and - an analysis of the safety zone, at the rear of the first vehicle, to detect the presence of the second vehicle follower; and: - as long as the first vehicle is not stabilised in a traffic lane, the system makes no further analysis; - if the second vehicle follower penetrates said safety zone at a distance less than said safety distance, the system: o displays a first warning message on the display; o identifies the second vehicle follower, the identification of the second vehicle follower comprising: ▪ the recording of the identity of the second vehicle follower; and ▪ the memorisation of the history of the distances, as long as the second vehicle follower remains in the safety zone. - if said distance decreases, displaying on the display a second warning message; and - If said distance decreases further, displaying on the display a third warning message and transmitting the identity of the second vehicle, previously recorded, to the remote server. - a device for measuring, where applicable, a clear distance at the rear of said first vehicle, between the first vehicle and a second vehicle that is following same; - a display disposed at the rear of the said first vehicle, for displaying a message as a function of the said distance, so that it is visible from the second vehicle follower, where applicable; - means for calculating a safety distance DS at least as a function of the speed of said first vehicle; - means (20, 9, 11, 12) for characterising a lane change of the first vehicle and for the system to analyse whether the first vehicle is stabilised in a traffic lane; - a device for recording an identity of the second vehicle follower and memorising a history of the distances as long as the second vehicle follower remains in a safety zone or at distance less than the safety distance DS, the display being, preferably, configured to display the identity; - a device for transmitting said identity to a remote server; - an analysis of lane change to check that the first vehicle is stabilised on a traffic lane; and - an analysis of the safety zone, at the rear of the first vehicle, to detect the presence of the second vehicle follower; - as long as the first vehicle is not stabilised in a traffic lane, the system makes no further analysis; - if the second vehicle follower penetrates said safety zone at a distance less than said safety distance, the system: o displays a first warning message on the display; o identifies the second vehicle follower, the identification of the second vehicle follower comprising: ▪ the recording of the identity of the second vehicle follower; and ▪ the memorisation of the history of the distances, as long as the second vehicle follower remains in the safety zone. o displays a first warning message on the display; o identifies the second vehicle follower, the identification of the second vehicle follower comprising: ▪ the recording of the identity of the second vehicle follower; and ▪ the memorisation of the history of the distances, as long as the second vehicle follower remains in the safety zone. ▪ the recording of the identity of the second vehicle follower; and ▪ the memorisation of the history of the distances, as long as the second vehicle follower remains in the safety zone. - if said distance decreases, displaying on the display a second warning message; and - If said distance decreases further, displaying on the display a third warning message and transmitting the identity of the second vehicle, previously recorded, to the remote server.