This manual reflects current thought on the best practices to employ in public transportation safety and security and the evolution from the long standing System Safety Program process, defined in the System Safety Program Plan (SSPP). This process was initially developed by NASA and the Department of Defense. The impetus for the development of a systems level approach came in the early 1970s with the expansion of subways to support the growth of major cities across North America. In the 1980s, the Urban Mass Transit Administration partnered with APTA to create a national program for the development of System Safety Programs to ensure that all the new transit systems could be designed and built using the best safety practices. Over the ensuing years this program expanded to Commuter Rail and Bus transportation. Download Document