Remote Sensing of Motor Vehicle Exhaust Emissions

European motor vehicle emission control legislation has not been effective in controlling emissions of all regulated air pollutants from light-duty diesel vehicles. Deficiencies in the current regulatory approach have been made clear in recent years. More and more diesel car manufacturers have been found to have deliberately circumvented the spirit of emission control legislation by optimizing systems to the very specific conditions of laboratory emission test programs, as opposed to designing effective control of emissions during real-world driving. Consequently, many diesel cars in Europe emit nitrogen oxides (NOx) at rates significantly higher than nominal regulatory limits when driven in real-world
conditions. These excess emissions have exacerbated urban air quality problems in European cities and have been linked to thousands of premature deaths each year.

Actions are now being taken to strengthen the European regulatory program for light-duty vehicles, including a transition to a more representative laboratory emissions testing procedure, the introduction of real-driving emissions (RDE) test requirements using portable emissions measurement systems (PEMS), and revisions to the existing type-approval and market surveillance framework. While these are positive steps, it remains to be seen whether provisions will not be circumvented again, in particular as vehicle systems can still detect when a car is being run through the new testing procedures. Therefore, authors argue, there is a need to complement with alternative emissions test methods in order to monitor and ensure the effectiveness of the European motor vehicle emissions control program. This paper considers one such method, vehicle emissions remote sensing, which has been used for more than 25 years to measure emissions from passing motor vehicles in real-world driving.

The purpose of the paper is threefold:

1. To review technical details of the vehicle remote sensing test method;
2. To describe the multiple types of emissions analyses that can be conducted with remote sensing data, and
3. To explore areas where remote sensing can supplement emission test methods currently used in the EU light-duty vehicle regulatory program.