European light duty vehicle emission legislation is gradually shifting the focus from test procedures with merely static test cycles, towards procedures including Real Driving Emissions (RDE), as they are a mean to achieve the European (NOx) emission reduction target. Hence a RDE trip must represent European driving behavior, such that «real world driving» emissions can be assessed. However, the usage of portable emission measurement systems has technical limitations. An alternative is testing on the chassis dynamometer in the laboratory. In order to cover a wide range of driving behavior to evaluate the real world driving emissions, a Random Cycle Generation methodology based on two Markov chains and real world measured data is developed. This methodology is used in order to develop the WLTP Random Cycle Generator Tool.