Overlay ECP brake system
Overlay ECP brake system means a brake system that has both conventional pneumatic brake valves and ECP brake components, making it capable of operating as either a conventional pneumatic brake system or an ECP brake system. This brake system can operate in either a conventionally braked train using the conventional pneumatic control valve or in an ECP braked train using the ECP brake system's CCD.
Source
49 CFR § 232.5
Scoping language
The definitions in this section are intended to clarify the meaning of terms used in this part.