DaimlerChrysler chooses SCR for trucks: After examining all the technological options available, DaimlerChrysler has chosen SCR (= Selective Catalytic Reduction) technology to meet future stricter emissions standards (Euro 4 and Euro 5). SCR-based aftertreatment lowers nitrogen oxide emissions and also reduces particulate emissions. SCR uses ammonia in an aqueous urea solution as a reducing agent to selectively convert toxic nitrogen oxides into harmless nitrogen and water vapour. On the demonstration vehicle (Mercedes-Benz Actros) the smaller AdBlue tank is clearly visible behind the front axle, next to the diesel tank.