Abstract: Proximity warning system (PWS) functions are integrated into the locomotive control unit (LCU) of an end of train (EOT) communication system. The PWS operation provides increased information to train crews relating to the location and movement of other trains in the area. The PWS functions are supported with the addition of a separate high speed modem which can access the LCU transmitter. A second radio receiver, the same frequency as the existing LCU transmitter, allows reception of transmissions from other PWS equipped locomotives. A location determination device, such as a GPS receiver, establishes current location and direction. The PWS operation is controlled by a microcontroller which, together with the existing LCU microcontroller, manages the control of the integrated system operation.