UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2000 TRAVERWOOD ROAD

ANN ARBOR, MI 48105-2498

 OFFICE OF

AIR AND RADIATION

July 29, 2011

MEMORANDUM

SUBJECT: Meeting with PACCAR

FROM: Angela Cullen

TO: Docket EPA-HQ-OAR-2010-0162

This memorandum documents a meeting held on May 3, 2011 between PACCAR and EPA. 

Paccar requested a meeting to discuss the tractor aerodynamic drag certification testing method. 

In the NPRM, the agencies proposed that tractor manufacturers use a two part screening 

approach for determining the aerodynamic inputs to the GEM. The first part of the proposed 

evaluation approach uses a bin structure characterizing the expected aerodynamic performance 

of tractors based on definable vehicle attributes. The first part would require manufacturers to 

assign each vehicle aerodynamic configuration to one of five aerodynamic bins. For each bin, 

EPA and NHTSA have already defined a nominal Cd. The five bins are “classic,” which 

incorporate few if any aerodynamic features; “conventional” which represent the average new 

tractor sold today; “SmartWay” which have added components to reduce drag: “Advanced 

SmartWay,” which have underbody airflow treatments, down exhaust, and other features, and 

“Advanced SmartWay II which incorporates technologies that are still in the prototype stage 

such as advanced gap closing. The second proposed evaluation uses aerodynamic testing. 

Manufacturers would be required to compare their test results with the bin Cds. If their test data 

shows a better or worse result than the Cd assignment, they would be required to certify to the 

correct bin. The agencies expressed an interested in working with the regulated industry to 

develop a primary test approach. The agencies proposed to allow Cd assessments with vehicle 

coast down testing, wind tunnel testing, computational fluid dynamics, and constant speed tests 

combined with good engineering judgment. There are two sub-categories for class 7 trucks: 1) 

low/mid roof day cabs; and 2) high roof day cabs. There are five sub-categories for class 8 

trucks: 1) low/mid roof day cabs; 2) high roof day cabs; 3) low roof sleeper cabs; 4) mid roof 

sleeper cabs; and 5) high roof sleeper cabs. 
2

Paccar asked that in addition to requests made by EMA/TMA to improve the aerodynamic drag 

coefficient test method and which are described in a memo to the docket several additional items 

be considered by the agencies in establishing the reference test method. Paccar stated the 

proposed changes would improve repeatability and accuracy and reduce the test burden on 

regulated entities. They requested the following:

o Closed road for coast down testing; 

o Standardized trailer gap at the centerline of the vehicle; 

o Specified height of the trailer at front and back; 

o Specified tractor tires (including mileage and other important parameters);

o The agencies identify and define parameters that have not been defined (such as data 

smoothing, frequency of calculation, etc.); 

o Recommend limiting grade to 0.1% (vs. 0.5% currently) because the gravitational effect 

of a 68,000 pound vehicle is a large contributing factor to low speed road load.