Gap measurement for vehicle convoying

A method of identifying a position of a back of a first vehicle using radar scenes received from a radar unit on a second vehicle, the method comprising:

• (a) estimating a position of the first vehicle relative to the second vehicle;
• (b) receiving a radar scene sample from the radar unit on the second vehicle, the radar scene including a set of zero or more detected radar object points, each radar object point corresponding to a detected object having a distance from the estimated first vehicle position;
• (c) identifying first vehicle radar point candidates within the set of received detected radar object points;
• (d) categorizing the first vehicle radar point candidates based on the distance of the corresponding detected objects from the estimated first vehicle position;
• (e) repeating steps (a)-(c) a multiplicity of times, whereby the categorized first vehicle radar point candidates include candidates from multiple sequential radar scene samples;
• (f) identifying the position of the back of the first vehicle based at least in part of the categorization of the first vehicle radar point candidates;
• and
• (g) determining an effective length of the first vehicle based at least in part on the identified back of the first vehicle.