In this paper, we have presented the cooperative free space optical (FSO) communication system with radio frequency (RF) backup as an application to the level crossing warning systems for Railways. Reliability and bit error rate (BER) performance has been carried out to ensure the performance improvement over single link. Cooperative FSO link continues to work in the presence of rain in which the RF system fails. BER performance improvement includes the study of various combining schemes including multiple gain combiner (MGC) which is simple and provides close to optimum performance. FSO system fails in the presence of fog whereas the RF system continues to work. The complementary nature of the system ensures that one of them gives desired performance in the presence of rain/fog. The effect of equipment failure, turbulence, pointing error, fog and rain has been studied in reliability analysis. Different relaying techniques and various combining techniques are the part of study in BER analysis. With the use of reflect and forward relaying scheme including cyclic redundancy check and 3 out of 5 majority voting scheme, we can achieve the desired tolerable hazard rate which meets the international standards of safety integrity level 4.