Work tractor

A working tractor comprises a self-driven first vehicle and other vehicles which sequentially move in the working direction at theoretical intervals, the working tractor is provided with an interval monitoring device for outputting interval signals, the interval monitoring device is provided with a beam source and a sensor assembly for detecting radiation of the beam source, the vehicle serves asa source vehicle to carry the beam source, and the sensor assembly is used for detecting radiation of the beam source. The beam source emits electromagnetic radiation toward another vehicle as a target vehicle such that radiation is present only in a beam space extending in a first angular range about a first beam space axis and in a second angular range about a second beam space axis. The sensorassembly extends along a sensor axis and is arranged on a target vehicle, a reference detection area on the sensor assembly is irradiated by a beam source, and the sensor axis is obliquely arranged around an inclined axis para