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An unobstructed line-of-sight (LOS) channel has to be guaranteed for the outdoor traffic light to vehicle visible light communication system. The performance of such LOS link in an empirical outdoor environment hasn't been characterized experimentally. In this paper, a thorough link characterization is carried out. Possible interference in the LOS link is first characterized, including both background solar radiation and artificial light sources. The frequency response of commercial-off-the-shelf (COTS) LED traffic light lamps as transmitter devices is then investigated, which reveals a modulation bandwidth of 3~5 MHz for common LED traffic lights. Also the theoretical LOS path loss model is proposed and validated by the measurement results. Lastly, the practical communication system performance based on the above characterization is evaluated, with results shown that a data rate of 1 Mbit/s could be achieved at a distance of 75 m with a raw BER of 10-2 in the electronics noise limited case.