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The latest legislative tendencies for on-highway heavy duty vehicles forecast further tightening of the NOx emissions limits in the European Union and also in the US; a NOx limit of 0.02 g/bhp-hr – the so called ultra low NOx limit – has been already approved by the California Air Resources Board (CARB) starting MY2027. In addition, the already phased-in regulations regarding CO2 enforce also a continuous reduction in CO2 emissions resp. fuel consumption both in the EU and in the US.In order to meet low NOx emission limits, a rapid heat-up of the exhaust aftertreatment (EAT) system is inevitable. However, the required thermal management results in increased fuel consumption, i.e. CO2 emissions as shown in numerous previous works also by the authors. A NOx-CO2 trade-off for cumulative cycle emissions can be observed, which can be optimized by using more advance technologies on the engine and/or on the EAT side.In the present study a systematic investigation is carried out by means of modelbased holistic approach targeting the definition of optimal engine and EAT layout and thermal management calibration for future legislative emission limits.Using holistic engine and EAT concept development approach, conventional and advanced EAT layouts are tested. The advanced EAT layout consist of a close-coupled dual-stage SCR system which is directly coupled to the engine model. In order to explore the benefits of each layouts, the engine heat-up calibrations are varied and the resulting, cumulative NOx-CO2 emissions of the investigated cycle are compared and evaluated. Also, multiple improvement measures for engine are discussed and an outlook of future powertrain concepts is given.