Assessment of the monitoring methodology for CO₂ emissions from heavy duty vehicles : pilot phase test-campaign report and analysis of the ex-post verification options

Following a request from DG-Clima and DG-GROW, JRC launched a test-campaign in order to investigate the validity, accuracy and plausibility of the methodology proposed for the verification of the certified CO2 emissions from Heavy Duty Vehicles (aka ex-post verification methodology). In addition 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 four Euro VI trucks, both on the chassis dyno and on the road with the aim of understanding the advantages and disadvantages of different approaches proposed. Two main verification approaches were investigated, steady state measurements in chassis-dyno / controlled conditions, and measurements under transient conditions on chassis-dyno and actual on-road operating conditions. The official simulation software (VECTO) was used for simulating the operation of vehicles under the different test conditions. The key conclusion of the test campaign is that an ex-post verification method which is based on transient, on-road tests is possible for trucks and comes with the advantage that it could potentially cover also other vehicle types which are difficult to be validated under steady state conditions in a laboratory or on a test track under controlled conditions. 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 road, and establish the necessary acceptance and rejection margins for any such validation. 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. VECTO results should be periodically controlled and assessed in order to make sure that its CO2 estimates remain representative and minimize the possibility that discrepancies will occur in the future between the officially reported and actually experienced fuel consumption.