A system includes a prime engine connected to a prime engine exhaust stack that receives prime engine exhaust, a mixing duct section connected to the prime engine exhaust stack, a head-end power (HEP) generator connected to an HEP generator exhaust pipe that receives HEP generator exhaust, a single urea injector, and a selective catalytic reduction (SCR) system. The HEP generator exhaust pipe is connected to the mixing duct section, and the single urea injector injects urea into the HEP generator exhaust pipe upstream of the mixing duct section. The HEP generator exhaust and prime engine exhaust merge in the mixing duct section to form a merged exhaust that is received by the SCR system.