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Aerodynamic drag testing is a key component of the CO2 certification schemes for heavy-duty vehicles around the world. This paper presents and compares the regulatory approaches for measuring the drag coefficient of heavy-duty vehicles in Europe, which uses a constant-speed test, and in the United States and Canada, which use a coastdown test. Two European trucks and one North American truck were tested using the constant-speed and coastdown methods. When corrected to zero yaw angle, a difference of up to 12% was observed in the measured drag coefficients from the US coastdown procedure and the EU constant-speed test.

Due to the diversity of Heavy Duty Vehicles (HDV), the European CO2 and fuel consumption monitoring methodology for HDVs will be based on a combination of component testing and vehicle simulation. In this context, one of the key input parameters that need to be accurately defined for achieving a representative and accurate fuel consumption simulation is the vehicle's aerodynamic drag. A highly repeatable, accurate and sensitive measurement methodology was needed, in order to capture small differences in the aerodynamic characteristics of different vehicle bodies. A measurement methodology is proposed which is based on constant speed measurements on a test track, the use of torque measurement systems and wind speed measurement. In order to support the development and evaluation of the proposed approach, a series of experiments were conducted on 2 different trucks, a Daimler 40 ton truck with a semi-trailer and a DAF 18 ton rigid truck.

Following its commitment to reduce CO2 emissions from road transport in Europe, the European Commission has launched the development of a new methodology for monitoring CO2 emissions from heavy-duty vehicles (HDV). Due to the diversity and particular characteristics of the HDV sector it was decided that the core of the proposed methodology will be based on a combination of component testing and vehicle simulation. A detailed methodology for the measurement of each individual vehicle component of relevance and a corresponding vehicle simulation is being elaborated in close collaboration with the European HDV manufacturers, component suppliers and other stakeholders. Similar approaches have been already adopted in other major HDV markets such as the US, Japan and China. In order to lay the foundations for the future HDV CO2 monitoring and certification software application, a new vehicle simulation software was developed, Vehicle Energy Consumption calculation Tool (henceforward VECTO).

In the future, similar to passenger cars, newly registered European heavy duty vehicles shall be labelled with the fuel consumption in typical driving cycles, determined at standardised conditions. This shall improve the comparability of the vehicles and motivate manufacturers to apply more fuel-saving technology. Therefore, a multi-stage certification procedure has been developed by a consortium of European laboratories under the leadership of the Institute for Internal Combustion Engines and Thermodynamics of TU Graz. It is based on a simulative approach and consists of: On-road measurement of driving resistances; determination of drivetrain losses; power demand of engine auxiliaries and other consumers; generation of an engine fuel consumption map from the engine's type approval tests; development of several driving cycles, typical for different vehicle applications; and a proposal for a calculation method of fuel consumption.