electromagnetic radiation object position detection system and method are disclosed for detecting when an object is located in the path of a powered sliding gate . in a preferred embodiment , polarized microwave radiation is emitted from a source fixed relative to the sliding gate . this radiation is projected along and spaced ahead of the leading edge of the sliding gate by a redirecting means which moves with the gate . a second redirecting means also moves with the gate and redirects the radiation back to a detector fixed relative to the sliding gate which provides a signal when this radiation is detected . the presence of an object in the path of the sliding gate is indicated by the blockage of radiation in the beam moving with the leading edge of the sliding gate .