Explanation of the TRUE real-world passenger vehicle emissions rating system
The TRUE initiative seeks to supply cities with data regarding the real-world emissions of vehicle fleets, and equip them with technical information that can be used for strategic decision-making. One of the key objectives of TRUE is to raise awareness of the magnitude and scope of excessive real-world vehicle emissions. This is the second paper in a series of technical papers, focusing on development of the TRUE rating system which rates vehicles on real-world NOX emissions, as measured by remote sensing data.
The TRUE rating system is designed to concisely convey the relative magnitude of real-world emissions from Euro 3 through to Euro 6 vehicle models under a wide range of operating conditions and driving behaviors. Factors included in the ratings include emission control system deterioration, defective parts, software that increases emissions in conditions outside of those typically covered by the regulation, and improvements by recalls and retrofits.
The TRUE ratings system uses green, yellow, and red symbols to indicate Good (green), Moderate (yellow), or Poor (red) emissions performance. An overview of the initial ratings in the figure below shows the share of vehicle families receiving a green, yellow, or red rating grouped by fuel type and Euro standard. From Euro 3 to Euro 5, all diesel families are rated red. For Euro 6 vehicles, approximately a 10th of diesel families are rated yellow. In contrast to diesel vehicles, the TRUE ratings for petrol vehicles improve with each successive emissions standard. Only 3% of Euro 3 petrol vehicle families receive a green rating, but almost two-thirds of Euro 6 petrol vehicle families are rated as green and none are rated as red.
The three-color TRUE rating system was developed as an easy-to-use tool for identifying the lowest and highest emitting vehicles in the fleet. The TRUE rating can help car owners know whether their car is clean and can help potential buyers identify the cleanest available cars for purchase (for NOx). The ratings represent, as best as is possible, measurements of real-world emissions.