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Assessment of the Measurement Methodology for CO2 Emissions from Heavy Duty Buses and Coaches


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Abstract: 

After the adoption of the CO2 Certification Regulation on the determination of the CO2 emissions and Fuel Consumption of Heavy-Duty trucks, the European Commission has decided to proceed with the preparation of a new regulatory initiative for the certification of CO2 emissions and Fuel Consumption from Buses and Coaches. The new methodology is intended to be a continuation of the Heavy-Duty Vehicles CO2 certification regulation and it will be based on a combination of component testing and computer simulation of the vehicles' Fuel Consumption. Following a request from DG-Clima, JRC launched a test-campaign in order to investigate the possibility to extend the methodology proposed for the verification of the certified CO2 emissions from Heavy Duty trucks to Buses and Coaches. In addition, the scope of the test campaign was to demonstrate the representativeness of the CO2 emissions calculations made by the official simulator (VECTO) by comparing against the actual performance of vehicles. Experiments were conducted on two Euro VI Buses, one Interurban Bus and one Coach, both on the chassis dyno and on the road, with the aim of understanding the advantages and disadvantages of different approaches proposed. The official simulation software (VECTO) was used for simulating the operation of vehicles under the different test conditions. The principal conclusion of the test campaign is that an ex-post verification method which is based on transient, on-road tests is possible also for Buses and Coaches. However, there is a clear need to work on the details of the test protocol to be finally implemented, define boundary conditions for transient tests on the road, and establish the necessary acceptance and rejection margins for any such validation. Additional care should be paid to the auxiliary components as they are a special part of Buses and Coaches and contribute highly to the overall Fuel Consumption of these vehicles. Finally, additional testing is necessary in order to calculate accurately any systematic deviation between the officially reported, simulated, CO2 values and those actually occurring in reality.

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