A detection system includes a ranging-sensor and a controller-circuit. The ranging-sensor is configured to detect objects proximate to a host-vehicle. The controller-circuit is in communication with the ranging-sensor. The controller-circuit is configured to determine that a trailer is being towed by the host-vehicle and determine a trailer-distance between the host-vehicle and a front of the trailer based on a distance to a first-group of objects detected by the ranging-sensor. The first-group is characterized by a first-distance indicated by the ranging-sensor. The controller-circuit determines an axle-distance between the front of the trailer and a trailer-axle based on a second-group of objects. The second-group is characterized by a second-distance indicated by the ranging-sensor. The controller-circuit determines a trailer-length based on the trailer-distance and the axle-distance.