Figure 6.
Normalized average net contribution of tested vehicles to number concentrations for (a) HD vehicles (no filtration systems) and (b) LD vehicles (no filtration systems).
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.