As part of the Euro 6 legislation in the EU the newly introduced RDE (Real Driving Emission) tests force vehicle manufacturers to reduce the engine emissions under real driving conditions. Vehicles have to fulfill the RDE legislation limits at an altitude up to 1300m above sea level and at temperatures between -7 and 35 °C. The legislation in other countries goes even further, for example China with RDE tests in up to 2400 meters altitude. The ambient conditions where a vehicle can be tested vary depending on the location and can change from day to day. In contrast, simulating these conditions on a component test stand or a chassis dynamometer allows for reproducible test results and enables vehicle manufacturers to decrease cost-intensive “on the road” testing to a minimum. With the integration of an altitude simulator and emission measuring equipment it is possible to simulate test drives with a given set of ambient parameters as many times as wanted in order to optimize the behavior of the vehicle and single components. Additionally, the WLTC (Worldwide harmonized Light vehicles Test Cycle) was introduced as a supplementary testing requirement in September 2017. The goal is to harmonize light-duty testing on a global basis. Emission legislation will also become even more challenging in the near future by the inclusion of the in-service conformity testing.