Worldwide use of remote sensing to measure motor vehicle emissions

Remote sensing is potentially the best option for fleet emissions monitoring, the development of an emissions factor, the identification of individual high- or low-emitting vehicles, and the screening for groups of high-emitting vehicles for market surveillance.

The development and use of remote vehicle emissions sensing has been growing in recent years. Data has been collected from all continents except Antarctica, with more than 1 million measurements per year collected in China, the United States, Hong Kong, and Korea, and more than 1 million measurements since 2010 in India. In Europe, data collection activities have been mostly in western countries—with more than 1 million measurements since 2010 in Spain—and northern countries.

The pollutants measured varied across the different remote sensing testing programs. The large majority measured nitrogen oxide (NO), hydrocarbons (HC), and carbon dioxide (CO₂) while more than half the programs measured (nitrogen dioxide) NO2, carbon monoxide (CO), and some measure of particulates. Most of the applications have focused on research and overall fleet emission trends. In some countries, remote sensing is moving into identification of high-emitting vehicle groups for market surveillance and identification of individual high- and low-emitting vehicles to assist with periodic vehicle emission inspections. The United States and China are leaders in remote sensing deployment and are demonstrating how remote sensing can contribute to identification of and enforcement against high-emitting vehicles. Recently there has been a significant increase in the use of and interest in remote sensing in the European Union.

There are multiple opportunities to increase the use of remote sensing data. Countries and regions should ideally explore ways to reduce barriers to remote sensing, such as improving equipment and data analysis, as well as decreasing the cost and addressing other logistical hurdles. Recommendations for ways to lower remote sensing barriers include:

• Independent validation of the various technologies available on the market.
• Development of national and international centralized databases on vehicles’ registration data, accessible quickly and at low cost while respecting privacy concerns.
• Continued development of technologies that allow unmanned operation while lowering their maintenance cost.
• Extending the scope of measured gases.
• Devising and improving methods to use real-world remote sensing to enhance emission factors used for air quality modeling and other applications.
• Scaling up the amount of remote sensing and number of measurement sites to increase the proportion of the in-use fleet that is regularly measured.

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