The purpose of this paper is to provide NOx and CO2 emissions data from the 2003-2005 model year (MY)
heavy-duty trucks. The 2003-2005 trucks are still widely in service in the United States and do not have either diesel particulate filters (which became common after US 2007 regulations) or selective catalytic reduction
(which was adopted only since the 2010 regulations). Some may favor using these older trucks in service because they are simpler in controls. The average vehicle miles travelled (VMT) by heavy duty trucks (defined as
heavier than 26,000 lb) that are older than 5 years is more than 40% of the total VMT by all the heavy duty
trucks according to the recently released Vehicle Inventory and Use Survey (VIUS) data [1]. The 2003-2005
MY trucks are about 7 - 9 years old and these trucks contribute about a sixth of the total VMT by all heavy duty
trucks in the US. However, the emissions contribution from these trucks will be disproportionate to their VMT
contribution due to the new stringent regulations. For example, these older trucks have NOx emissions about 10
times that of the new trucks due to new regulations. Hence, they contribute to total NOx emissions at about 3
times that of the new trucks.