Since I worked on this SW I have to clarify a bit.<p>Lab testing of course does emulate real-world driving conditions. Otherwise your tests will not be worth much. Either you play back a recorded existing course (RPS - road profile sequences) or you simulate it, simple steady state and transient cycles. We are automating reproducible test conditions.<p>But we are here only talking about the different emission tests, where we have 2 major philosophies. The european emission test tracks (NECD), which is also used in India and Asia, which is an highly abstract test with the engine alone driven by a similator simulating multiple real-world driving conditions (a few urban cycles) and the american test on a dyno with a real driver (with varying cycles), so that the american car manifacturers, who traditionally were not so good in designing emission-free engines could traditionally cheat by hiring the best drivers to pass the test.<p>So Americans have cheated historically the most, but apparently engine manifacturers which couldn&#x27;t catch up with modern diesel engine development had to cheat also. First it is trivial to cheat, since the test has to be done only once. This is entirely a political game to get the NOx and COx values down, but don&#x27;t harm their own industries. And esp. Americans seldom use scientifically based values.<p>And then you have cold starts in reality, which is mostly not tested in the emission cycles tests. Emissions will always be higher in the field than with a properly warmed up engine under lab conditions. So it&#x27;s no surprise that different measurement methods will lead to different results.