This document defines warning horn requirements that deliver the required audibility of approaching heavy rail vehicles. The requirements of this document do not apply to urban rail systems. NOTE 1 The requirements for exterior audible warning devices for urban rail vehicles are found in EN 15153 4. In the case of shunting heavy rail vehicle formations, the requirements of this document do not apply to the pushed vehicle(s). For this purpose, the following requirements are included: - functional and technical requirements of the warning horn as a component, - functional and technical requirements of the integration of warning horns into the vehicle, and - test requirements. Operational requirements and maintenance requirements for warning horns are excluded. NOTE 2 The requirements for the control of warning horns can be found in EN 16186 2.