Real Driving Emissions (RDE). Issues and challenges

Road mobility is essential to our society. It is the driving force behind economic development and one of the fundamental aspects of social cohesion, as it allows everyone freedom of movement. Although it is still the most widespread energy source for road mobility, the internal combustion engine faces environmental problems. This is why now, more than ever, the need to strike a balance between the natural intensification of road mobility and environmental protection is obvious. The significant progress made by the internal combustion engine over the past period has not dispelled concerns about its long-term effects on the environment. Moreover, recent discussions on global warming and the impact of pollutants on human health have led to increasingly stringent automobile homologation regulations. In the future (more so than in the past), carmakers will have to face up to a dual challenge: reducing pollution in large urban areas, but also reducing greenhouse gas emissions. This latter challenge is not yet part of the homologation procedure, but it is of the utmost importance in reducing global warming. In addition to these two challenges, there is also the constraint of limiting the total cost of vehicle ownership, and that of reducing driving pleasure. As far as homologation is concerned, the rules changed in September 2017: a more representative driving cycle for real traffic (WLTC replaced the well-known NEDC cycle) in the homologation procedure under laboratory conditions on the chassis dynamometer; in addition, the famous RDE (Real Driving Emissions) procedure took its first steps.

In this context, this article will present the current passenger car homologation procedure: repeatable tests under laboratory conditions and real world driving conditions (RDE) tests to analyze the deviation from laboratory results. Some RDE case studies will also be included to illustrate the RDE issue.

A first obvious conclusion is that the RDE procedure is a major step forward, because over the years it has been shown that the requirements on driving cycles performed on a chassis dynamometer under laboratory conditions are not sufficient. An equally obvious conclusion is that the RDE procedure signifies a paradigm shift in the development and homologation testing process, which can be summed up simply as follows: from repeatability (under laboratory conditions) to statistical probability (RDE – under real driving conditions). This necessary change is accompanied by significant complications which will be detailed in this article.

Lastly, we emphasize that this text has its origins in the current social context, which is characterized by an unprecedented green effervescence, but which absolutely must be properly managed and controlled on all five continents,...