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Initiatives have been and will be taken to define very strict emission limitations for Heavy-Duty (HD) urban transport vehicles in Europe. This will probably led to a class of very clean, so-called, Enhanced Environmentally friendly Vehicles (EEV). This paper presents an overview of the current and the (expected) future emission legislation for this type of vehicle together with the different technology that can be used for the development of internal combustion engines for these vehicles. A number of engine concepts, based on the experience of developing these concepts, are described and compared both from a technological and economic standpoint. It can be concluded that EEV emission limits can be achieved with advanced diesel engine concepts as well as with gas engines. From the economical viewpoint it can be concluded that gas engines can compete with diesel engines.

A study was carried out in which most aspects of dimethyl-ether (DME) as an automotive fuel were critically evaluated. DME appeared to have positive characteristics from both the energy supply and security point of view as from an exhaust emissions point of view. DME can be made from a wide variety of fossil feedstock, among which natural gas and coal, and from renewable feedstock and waste. These energy sources will last longer than crude oil. A comparison was set up between DME and other regular and alternative fuels. This comparison covers engine exhaust emissions and well to wheel energy efficiency and CO2 emissions. It appeared that the exhaust emissions of DME fuelled engines are comparable to lean burn gas engines (heavy-duty) or otto engines with three-way catalyst (light-duty). With respect to well to wheel CO2 emission DME is rated equal to the diesel engine. Compared to natural gas DME measures from about equal (heavy-duty) to about 10% better (light-duty).