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Integrating retrofit technologies into the existing drayage fleet can achieve significant reductions in 

emissions depending on the technology selected. 

What is the challenge?

With the development of cleaner engine 

technologies, the emission profiles of diesel trucks 

have improved over time. These cleaner 

technologies take time to work their way into the 

existing truck fleet however. The drayage fleet, 

since it typically consists of the oldest trucks on the 

road, is the last to see improvements from the 

cleaner technologies added to new trucks. 

Consequently, areas served by the drayage fleet 

are subject to higher pollution levels. 

What is the solution? 

Engine replacement will capture the technological 

improvements recently introduced, however it is 

often prohibitively expensive. If engine 

replacement is not an option, there are a number 

of retrofit technologies or fuel additives that can 

improve emissions from older trucks. Retrofit 

control devices tend to be engine-specific, with 

options for older trucks remaining more limited 

than for newer models. Proper maintenance and 

use of the retrofit device is required to ensure 

continued effectiveness of these devices on older 

higher emitting trucks. 

The U.S. Environmental Protection Agency has 

signed a Memorandum of Agreement (MOA) with 

the California Air Resources Board (CARB) 

establishing reciprocity in the verification of 

emissions control technologies. There are

approximately six technologies/additives available 

for pre-1988 engines on the lists of verified 

technologies for both CARB and EPA. 

The results are in . . . 

The technologies/additives that are approved for 

use in older trucks are listed in the table below 

along with the expected emissions improvement.

All of these options come with slight fuel efficiency 

penalties. Retrofit devices applied to older engines 

have the potential to reduce particulate matter 

(PM), carbon monoxide (CO) and hydrocarbons 

(HC) whereas devices that reduce nitrogen oxides 

(NOx) or carbon dioxides (CO2) are still being 

developed. Also, these devices must be 

maintained properly and operated using low sulfur 

(500 ppm or less) on-highway fuel. Adding 

biodiesel is one of the few options to improve CO2

emissions from older trucks, however biodiesel 

potentially increases NOx emission rates. 

Next steps

The technology to improve the emissions profile of 

older trucks exists. It is simply a matter of paying 

for it. There are no efficiency improvements that 

accrue to those adopting the new technologies, 

requiring the provision of incentive mechanisms. 

California’s Carl Moyer Program helps fund 

technologies that achieve greater than required 

emission reductions. This government funded 

program is one mechanism that could speed the 

adoption of retrofit devices. 

The EPA’s Voluntary Diesel Retrofit Program Web 

site highlights information for fleet 

owners/operators considering retrofit options for 

their vehicles, and can be found at: 

www.epa.gov/otaq/retrofit/overview.htm. 

Percent Emissions Reductions 

Manufacturer Technology PM CO NOx HC 

Engelhard CMX Catalyst Muffler 20 40 n/a 50 

Lubrizol PuriNOx 

Water emulsion fuel 16 to 58 -35 to 33 9 to 20 -30 to -120

Lubrizol Engine Control Systems AZ Purimuffler 

AZ Purifier 20 40 n/a 50 

Various Biodiesel (1 to 

100%) 0 to 47 0 to 47 0 to -10 0 to 67 

Various Cetane Enhancers n/a n/a 0 to 5 n/a 

 Johnson Matthey CEM Catalyst Muffler 20 40 n/a 50 

A Glance at Clean Freight Strategies: 

Retrofit Devices for Drayage 

U.S. EPA Office of Transportation & Air Quality ! EPA420-F-06-003 ! (734) 214-4767 phone ! smartway_transport@epa.gov ! www.epa.gov/smartway