Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Mechanical and Aerospace Engineering

Committee Chair

Arvind Thiruvengadam

Committee Co-Chair

Marc C. Besch

Committee Member

Marc C. Besch

Committee Member

V’yacheslav Akkerman


Currently in US, more than 26 percent of the total GHG emissions comes from transportation and mostly from heavy duty vehicles. Similarly, the European Council stated that 25 percent of the emissions comes from heavy duty transportation and they expect it to be further increased in the future. However, with the new coming regulations US EPA and European Council aiming to reduce the emissions by 80 percent in US and 60 percent in EU. In order to keep track and control the emissions, both authorities published new regulations and testing methods for certifying the new vehicles.

Aerodynamic testing is one of the most important part of certification since, aerodynamic drag is a major contributor of total road load acting on a vehicle which is highly related with emissions of a vehicle. Besides, simulation tools for certification such as “Vehicle Energy Consumption Calculation Tool (VECTO)” and “Greenhouse Gas Emission Model (GEM)” needs drag area ( ) as an input. Moreover, it is essential to determine the drag area correctly, therefore, emission of a vehicle, to be able to estimate the amount of total emissions from heavy duty vehicles.

Two different regulatory testing methods were published by US EPA and European Council to determine the drag area ( ) for certification of heavy duty vehicles. While US regulations requires “coast-down (CD)” test, EU regulations requires “constant speed (CST)” test. The objective of this study is to compare these two different regulatory approaches with their different assumptions. In order to be able to make a comparison of these two testing methods, CD and CST performed with same tractor and trailer combination, which is a Class 8 truck for US market, in same conditions.

Results yielded up to 9 percent difference between two methods. Possible cause of this difference can be listed as, the different assumptions of each testing method such as speed dependency of losses, different approaches for tire rolling resistance and some neglected or unaccounted loses. These possible reasons were also investigated individually in this study.