To support its activities in the field of conventional and hybrid vehicles, TNO has developed ADVANCE, a modular simulation tool for the design and evaluation of advanced power trains. In this paper the various features and the potential of ADVANCE are described and illustrated by means of two case studies. The first case describes an assessment of the potential efficiency and emissions improvements of an advanced series hybrid 'tram-like' bus for urban public transport in the year 2010, in comparision with a conventional bus. The bus is designed with a bipolar battery, an asynchronous electric motor and a generator driven by either a gas turbine or an LPG engine. In the second case the use of ADVANCE is described in the development of a system integrated power train for passenger cars, which makes use of a continuously variable transmission and an internal combustion engine (ICE), optimised for this transmission type.