TRB Transit Cooperative Research Program (TCRP) Report 115: Smartcard Interoperability Issues for the Transit Industry explores interoperability; identifies information needed by public agencies to implement smartcard payment systems interoperability; examines the necessary information flows; and outlines a set of functions needed for a standard public domain application programming interface (API) that may be used in the development of a uniform application protocol data unit (APDU). The report also includes a prototype for an API and an APDU that demonstrates this "proof of concept" for International Organization for Standardization-compliant Type A and Type B cards"--Publisher's description