Process for monitoring vehicles by a plurality of sensors

A process for monitoring vehicles (3, 4) on a road (2) comprising at least two traffic lanes (2a, 2b), by a system for monitoring vehicles (1) arranged in a fixed manner and comprising at least one radar sensor (10) and a second remote sensor (20) different from the radar sensor (10), the radar sensor (10) operating over a radar detection range (11) of the road covering at least two traffic lanes and emitting a stream of radar data representative of the detection of vehicles (3, 4) on the road (2), the second remote sensor (20) operating over a second detection range (21) of the road (2), the radar detection range (11) and the second detection range (21) being at least partially superimposed,

• wherein the second remote sensor (20) is an optical sensor emitting a stream of optical data representative of the detection of vehicles (3, 4) on the road (2), said optical sensor (20) being a time-of-flight optical sensor or an optical image sensor,
• the process comprising, in a continually repeated manner for a plurality of successive frames:
• a) temporal readjustment and spatial matching (S3) in a fixed shared spatial marker of the radar data and of the optical data in order to obtain a set of measurement points each assigned to first characteristics derived from the radar data comprising position measurements and speed measurements, and second characteristics derived from the optical data, the second characteristics comprising at least position measurements,
• b) determination of radar vehicle trackings (S4) from the first characteristics derived from the radar data and optical vehicle trackings (S5) from the second characteristics derived from the optical data, comprising:
• b1) a first segmentation which groups together, in first clusters, measurement points having first characteristics derived from radar data evolving in a similar way over several consecutive frames, the following over time of a first cluster forming a radar vehicle tracking (3, 4),
• b2) a second segmentation which groups together, in second clusters, measurement points having second characteristics derived from optical data evolving in a similar way over several consecutive frames, the following over time of a second cluster forming an optical vehicle tracking (3, 4),
• c) comparison of similarity between the radar vehicle trackings and the optical vehicle trackings, the comparison of similarity being based at least on the presence of shared measurement points over several consecutive frames, and matching of similar radar and optical vehicle trackings,
• d) elimination of the radar vehicle trackings for which no optical vehicle tracking is similar, in order to retain only the radar vehicle trackings for which at least one optical vehicle tracking is similar,
• the process comprising:
• e) monitoring a parameter derived from first characteristics of a retained radar vehicle tracking,
• and wherein, after the comparison of similarity between the radar vehicle trackings and the optical vehicle trackings, when an optical vehicle tracking does not have any similar radar vehicle tracking, the monitored parameter is derived from first characteristics derived from radar data corresponding to measurement points of the second aggregated of said optical vehicle tracking.