Best practices in emission control of in-use heavy-duty diesel vehicles

This report summarizes policy approaches to controlling in-use emissions from heavy-duty vehicles (HDVs), including freight trucks, buses, municipal government and other service fleets.

HDVs, while typically accounting for only a small percentage of a region’s vehicle fleet, emit a disproportionate share of total emissions of certain pollutants, especially particulate matter (PM) and nitrogen oxides (NOx). In addition, many HDVs have useful lifespans of 20 years or longer. Even when emission standards are implemented for new vehicles on an aggressive timeline, it typically requires decades before older, higher-emitting vehicles are retired from service and those standards finally cover the entire fleet. Managing emissions from legacy heavy-duty in-use fleets is therefore a key strategy for achieving rapid improvements in urban air quality.

The control of heavy-duty vehicle emissions presents unique challenges for policy makers. HDVs exist in thousands of different configurations and operate across varied duty cycles, so control programs must target different classes and types of vehicles. HDVs also play a critical role in virtually every sector within the economy, and older vehicles are often owned and operated by small business owners or self-employed individuals.

This report surveys a variety of emission control strategies for different categories of in-use HDVs, demonstrating that multiple effective solutions exist for most fleets in both developed and developing countries. Highlighting international best practices, it is meant to serve as a general reference guide for policymakers.