Concern over greenhouse gas (GHG) emissions and air quality has made exhaust emissions from passenger cars a topic interest at an international level. This situation has led to the re-evaluation of testing procedures in order to produce more “representative” results. Laboratory procedures for testing exhaust emissions are built around a driving cycle. Cycles may be developed in one context but later used in another: for example, the New European Driving Cycle (NEDC) was not developed to measure fuel consumption, but has ended up being used to that end. The new Worldwide harmonized Light vehicles Test cycle (the WLTC) will sooner or later be used for measuring regulated exhaust emissions. Legal limits for emissions of regulated pollutants are inherently linked to the test conditions (and therefore to the driving cycle); inter-cycle correlations for regulated pollutants are an important research direction. This study considers the current European cycle (the NEDC), the WLTC and the main US legislative cycle (known as the FTP-75). Quantitative comparisons of the three driving cycles are presented. The experimental study tested nine European vehicles over the three driving cycles, measuring regulated emissions according to the applicable test procedure. All testing was performed on a chassis dynamometer within a climate controlled laboratory, using a constant volume sampler (CVS) system. Both increases and decreases from the NEDC emissions baseline were observed. Inter-cycle changes in regulated pollutants were found to be up to two orders of magnitude greater than the corresponding changes in CO2 emissions.