The European emission standard Euro 4 comes into force in October 2006 for all newly registered commercial vehicles with a permitted GVW of 6 tonnes and above. Euro 5 will come into force in October 2009. There is also a voluntary EEV (enhanced Environmentally-friendly Vehicle) standard for commercial vehicles. Commercial vehicle engine manufacturers will also have to work to the US EPA standard and the Japanese JES standard. The standards focus on four types of emissions: carbon monoxide, non-methane hydrocarbons (NMHC), nitrogen oxides (NOx) and particulate matter (PM). The advantages and disadvantages of cooled exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) are outlined. The major truck, bus and coach manufacturers have opted for SCR. Blue Tec is the name of the enhanced diesel technology with a downstream emission control system developed for Mercedes-Benz and Setra buses and coaches. The requirement for an aqueous urea solution, trade name 'AdBlue', is discussed. The role of low emission buses in complying with PM levels specified in air quality standards is considered with reference to the Citaro natural gas buses from the Mercedes-Benz Bus and Coach Unit. DaimlerChryslers's work to develop a fuel cell drive system is described.
Abstract