Emissions from motor vehicles have been a subject of concern in urban areas, as great amounts of population have been permanently exposed to large amounts of pollutants, with intrinsic adverse health effects. In this context, in the last two decades, stringent emissions standards have been developed to control the maximum emission limits of the so called regulated pollutants. This continuous reduction of emission targets has imposed a great effort to engine and vehicle manufacturer in the development of technological solutions for emission limits compliance, which can be done by reducing engine-out emissions through improvements in combustion process and fuel management system, as well as by using aftertreatment devices in the exhaust system. Air pollutants of most concern for heavy duty engines - most often diesel engines - are particulate matter, oxides of nitrogen and volatile organic compounds, which have been continuously subjected to emission abatement measures in the context of international emission standards, basically European, North American and Japanese regulations (other countries’ emission regulation follow one of these, generally with some schedule delay). More recently, these norms have also focused CO2 emissions, hence, fuel consumption, as well as durability requirements. This have driven engine manufacturers to adopt clean, reliable, durable and affordable solutions, that ranges from optimization of combustion process - increased fuel injection pressure, injection timing and air management (air swirl, exhaust gas recirculation) - to exhaust aftertreatment devices (oxidation catalyst, selective catalytic reduction, diesel particulate filters, etc), which require improved fuel quality, specially low sulphur levels. All these requirements have resulted in two main cost impacts, i.e. incremental capital cost for the new hardware required on board the vehicle and increased operating costs, mainly arising from required fuel quality, reductant fluid consumption, maintenance procedures and special lubricant oil requirements. Urban transit vehicles are subjected to a special concern, as they are permanently subjected to the “stop and go” cycles with its inherent reduced engine exhaust temperature, that leads to the so called “Off Cycle” NOx emissions, which has been focused in the more recent (Euro VI and USA 2010) emission regulations. This work is supposed to present an overview of worldwide heavy duty engine emission standards associated with detailed assessment of technological strategies to allow their compliance, as well as the associated performance and cost analysis.