1. A trailer-detection system configured to determine a size of a trailer towed by a host-vehicle, said system comprising:a radar-sensor used to determine a range, an azimuth-angle, and an elevation-angle of a radar-signal reflected by targets associated with a trailer towed by a host-vehicle; and
a controller in communication with the radar-sensor, said controller configured to determine a size of the trailer towed by the host-vehicle based on the range, the azimuth-angle, and the elevation-angle of the radar-signal;
the controller further configured to determine a trailer-type based on the radar-signal; wherein
the trailer-type includes an enclosed-trailer, a utility-trailer, a utility-trailer-loaded, and a travel-trailer;
the controller further configured to define a three-dimensional trailer-boundary characterized as occupied by the trailer and thereby exclude the trailer from the zone proximate to the host-vehicle where objects are detected.