Abstract: Locomotive environmental system to be mounted in the roof of a cab for controlling the environment within the cab which includes a housing having an upper chamber arranged above the roof line of the cab and having one compartment for a condenser unit and another compartment for a compressor unit, a blower in the compartment housing the condenser unit for circulatng air through the condenser compartment and also through the compartment housing the compresser unit, a lower chamber arranged below the roof line of the cab and housing an evaporator unit for the system together with blower means for circulating air through the lower chamber and the cab, wherein the motors for the compressor unit and the blower associated with the condenser unit are driven by the same source of variable power.