Prag AES-APU [Automatic Engine Shutdown and Auxiliary Power Unit] system is designed to provide substantial fuel saving and reduce emissions of Diesel-Electric Locomotives by automatically shutting-down of main locomotive engine on idling along with continuous monitoring of critical parameters.

The system includes a small diesel engine coupled with a low capacity compressor and alternator that perform the function of maintaining main reservoir air pressure and keeping the locomotive batteries charged while the main engine is shutdown. The equipment is supplied complete with controls, sensors, accessories, and application software.

It is estimated that by preventing unwanted locomotive idling the Prag AES-APU would provide fuel saving of up to 150 – 200 Litres per locomotive per day, which translates to more than US$ 30,000 per locomotive per annum in addition to reducing idling emissions by more than 25%.