A steering wheel movement sensing apparatus (20) for an agricultural vehicle (5) comprising a magnetic ring configured to fit around the steering column (13) such that it turns in unison with the steering wheel (12). The minimum number of magnetic poles (21) on the ring is not defined, but a ring having at least 36 poles enables the movement sensor to detect steering wheel movement of 10 degrees. At least two hall-effect sensors (23, 24) fixed in a stationary position adjacent to the magnetic ring generate signals of fluctuating value as the magnetic poles (21) pass enabling wheel movement and the extent of wheel movement to be derived. By specifically adjusting the position of the hall-effect sensors (23, 24) in relation to each other, the resultant output signals can also be used to determine the direction of movement of the steering wheel (12). Outputs from the sensing apparatus (20) can be used to disengage an automated vehicle guidance system (100) upon detection of steering wheel movement and to provide input to a self-cancelling turn signal system (50).
