Current Heavy Duty testing is performed almost exclusively on engine dynamometers. The limitations of this method to obtain detailed emission data for heavy duty vehicles operating in the field are widely known. The wide variety of vehicles into which an engine type may be fitted and the disparate operating conditions that the vehicle is then subject to, mean that the real environmental impact of heavy duty vehicles can never be established.A Variable Temperature Emissions Chamber (VTEC) has been developed and used for chassis dynamometer testing of numerous road vehicles right up to Double Decker Buses. This facility enables accurate emissions data to be measured for specific vehicles in their real operating environments. The facility is equipped to simulate ambient temperatures from -30°C to + 50°C and with a high volume, speed tracking air flow.Driving cycles have been developed for buses and trucks, both from detailed on-road data logging and from simulated operations.The paper will discuss the current position in Europe and present the new test methods with detailed emissions results of aftertreatment products, developed to reduce heavy duty vehicle emissions in the field. The latest techniques in particulate size measurement have been applied to these vehicles and data will show how this has been used to evaluate particulate reduction methodologies on specific vehicle applications in order to engineer optimum solutions.