Orthogonal frequency division multiplexing (OFDM) is a transmission technique which divides a given frequency band into subbands such that the subcarriers are mutually orthogonal. Because of its favourable transmission properties, OFDM is widely used in wireless communications. Recently it was shown that it is possible to extract information about distance and speed of obstacles from OFDM scatterings as in a radar system. The combination of communications and radar in a single OFDM system for automotive applications was named OFDM Radar. In this paper a simple multi user access scheme for OFDM Radar is proposed and its implications on radar detector design are discussed. The proposed scheme is a variant of OFDMA based on the idea that each user chooses independently a subset of the available OFDM carriers for transmission. The chosen subcarriers can be spaced arbitrarily. A suitable detector which is furthermore capable of multiple target detection is derived and its performance in various scenarios is demonstrated using Monte Carlo simulations.