For over a decade, the EU has required in-service conformity testing of heavy-duty road vehicles. This paper briefly discusses the practical aspects of the test requirements, how they have evolved and how they compare to other precedents, such as the heavy-duty engine dynamometer-based type approval testing procedure, as well as broadly equivalent EU requirements for light duty vehicles. Emissions requirements for heavy-duty vehicles are work-specific, but based on standard test results a range of other parameters can be calculated to yield distance-specific, tonnage-distance specific, CO2-specific and (gravimetric) fuel-specific results. At present, CO2 and fuel consumption are not subject to any limits per se during on-road testing (and this is the case for both heavy and light duty vehicles); nevertheless, the aforementioned parameters must be measured and such results can be of interest for a variety of reasons. Insightful results in the form of fuel-specific emissions of pollutants, as well as work-specific fuel/energy consumption and the resulting empirical efficiency coefficient can all be calculated based on the standard result set commonly recorded during such testing. In this study, the factors mentioned above are introduced and discussed and sample test results are analyzed. The test results were obtained by carrying out the aforementioned EU test procedures on several heavy-duty vehicles with varying payloads (and with various powertrains, using Diesel or CNG fuel). The aforementioned metrics are used to characterize and normalize the results and compare them to various precedents. Comparisons are made with the case of light duty vehicles, their laboratory and on-road test procedures and the emissions limits they are subject to according to EU requirements.