Study on Fuel Economy and Nox Emissions of Medium Duty Hybrid Truck in Real Traffic Conditions

Hybrid trucks have now started to penetrate the Japanese market. To investigate their advantages for fuel economy and exhaust emissions, a real time on-board measurement system for fuel economy and NOx emissions was mounted in a medium duty hybrid truck with a capacitor system. Running tests were carried out with various payloads on roads. The results demonstrated the advantages of the hybrid truck in real traffic conditions. Fuel economy was improved on urban and suburban roads, as compared to a base diesel vehicle. The hybrid truck showed less NOx emissions during acceleration at starting, whereas, acceleration of diesel vehicles may cause intensive localized NOx pollution of roadsides, in places like intersections. In order to fully demonstrate the advantages of the tested hybrid truck, it was important not to use running conditions with infrequent stops, such as those on a highway, or running conditions in which less brake energy recovery can take place, such as those in a traffic jam, where it is hard to recover brake energy even though frequent stops occur. In addition, further reduction of NOx might be obtained by optimizing engine operation in the diesel engine running mode of the hybrid truck.