U.S. Department 

of Transportation

Research and

Innovative Technology

Administration

Volpe National Transportation Systems Center

May 9, 2011

MEMORANDUM

SUBJECT: Ex parte meeting with 

FROM: Coralie Cooper, Volpe

TO: Docket No. NHTSAThis memorandum documents a meeting held on Wednesday, March 

Manufacturers Association/Truck Manufacturers Association

proposed fuel efficiency and greenhouse gas standards for medium

engines for model years 2014-2018. 

aerodynamic drag certification testing method 

EMA: Tim Blubaugh, David Kayes, Andrea Brown, Dan Kieffer, Don Keski

Greszler

EPA: Byron Bunker, Angela Cullen, Cleophas Jackson, 

DOT: Coralie Cooper and Maurice Hicks

In the NPRM, the agencies that propos

determining the aerodynamic inputs to the GEM

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 toda

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 test results obtained using one of 

fluid dynamics, and wind tunnel testin

result than the Cd assignment, they would be required to certify to the correct bin. 

1

Volpe National Transportation Systems Center

eeting with the Engine Manufacturers Association

Volpe

-2010-0079

This memorandum documents a meeting held on Wednesday, March 3, 2011 between 

/Truck Manufacturers Association (EMA/TMA), EPA, and DOT

proposed fuel efficiency and greenhouse gas standards for medium- and heavy-duty vehicles and 

2018. Specifically, EMA/TMA requested a meeting to discuss the tractor 

aerodynamic drag certification testing method proposed in the NPRM. The attendees included:

Tim Blubaugh, David Kayes, Andrea Brown, Dan Kieffer, Don Keski-Hynilla, Rick Mihelic, Tony 

Angela Cullen, Cleophas Jackson, Arvon Mitcham, Julian Davis

nd Maurice Hicks

proposed tractor manufacturers use a two-part approach for 

determining the aerodynamic inputs to the GEM model. 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 

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 

as advanced gap closing. 

The second proposed evaluation uses aerodynamic testing. Manufacturers would be required to 

obtained using one of several approaches including coast down, computational 

wind tunnel testing) with the bin Cds. If their test data showed a better or worse 

result than the Cd assignment, they would be required to certify to the correct bin. In the proposal, t

55 Broadway

Cambridge, MA 02142

, 2011 between the Engine 

EPA, and DOT regarding the 

duty vehicles and 

Specifically, EMA/TMA requested a meeting to discuss the tractor 

The attendees included:

Hynilla, Rick Mihelic, Tony 

part approach for 

. 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 

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; 

y; “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 

The second proposed evaluation uses aerodynamic testing. Manufacturers would be required to 

coast down, computational 

a better or worse 

In the proposal, the 
2

agencies stated that the SAE J2263 coastdown procedures would be the primary testing tool but said we 

were interested in working with the regulated industry to develop a primary test approach. 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. 

EMA/TMA asked that, first, manufacturers be allowed to use the in-house test that is currently used for 

aerodynamic assessment, rather than being required to adopt a test method they don’t currently use. 

The reason for this request is that manufacturers have gathered data for truck models and have gained 

experience using their in-house testing methods. They stated it would be costly – both financially and 

from the standpoint of time – to have to re-test vehicle models on a new aerodynamic test method. 

They asked that manufacturers be allowed to correlate their in house test method results to a reference 

test. This, they stated, would allow manufacturers to use all of the data they have previously collected 

on aerodynamic drag. In response, the agencies said they are likely to adopt a reference test method 

that can be correlated to in-house methods.

EMA/TMA said there is value in selecting a reference test that establishes a wind average Cd, since a 

wind average Cd is more representative of real world conditions than a zero yaw Cd. A wind average Cd 

estimates the impact of different angles of wind on the truck aerodynamics. In contrast, a zero yaw test

only estimates the impact from head on wind. EMA/TMA noted, however, that a wind average Cd can 

only be established through wind tunnel testing, which is expensive and can only be done in a limited 

number of locations in North America. For these reasons, EMA/TMA asked that coast down testing be 

established as the reference test. They stated that coast down testing is the most preferred method for 

a reference test since: 1) the test location is not restricted to one of a few locations but rather can be 

conducted at a number of locations at a relatively low cost; 2) it is a commonly used test and thus most 

of the data in the industry has been generated this way ; and 3) it is a relatively repeatable test if 

defined clearly. With some methods -- modeling for example -- software program differences could 

result in variations in test results from use of different software programs. 

EMA/TMA asked that if the coast down method is chosen for reference testing, several changes be 

made to reduce variability test to test, to reduce the cost to manufacturers for testing, and to remove 

unnecessary or redundant elements of the proposed method: 

o Request increase in allowable speed in aero reference method from 62 mph to 70 mph;

o Request agencies define the rotational inertia of trailer tires for the reference test 

method;

o Request removing yaw calculation that is part of the SAE 2263 procedure;

o Request taking the anemometer off of front of truck for aero testing, and test at wind 

speeds of less than 5 mph;

o Request to run trailer empty in reference test rather than loaded;

o Request to use CdA rather than Cd;

o Request limiting grade to 0.1% of road grade.
3

The agencies agreed to evaluate U.S. wind speed data, data on road grade, and coast down test data 

that will be available through an EPA testing program to determine whether the above changes are 

appropriate for the final rule. The agencies also agreed to clarify language in the final rule that describes 

inputs to the GEM model for aerodynamic drag. 

In addition, EMA/TMA made the following two requests with regard to high roof trucks:

1. That a high roof day cab drag coefficient be estimated by assuming the coefficient is 7.8% worse 

than a high roof sleeper cab. Response: EPA agreed to evaluate CBI data on this issue.

2. Changes to GEM to account for the situations where real-world fuel saving measures, like 

downsizing an engine, may show up as fuel consumption increases in GEM due to marginally 

worse aerodynamics may be marginally worse . Response: The agencies agreed to evaluate this 

issue.

With regard to mid and low roof trucks, EMA/TMA made the following two requests:

1. That low and mid roof sleepers be tested “bobtail,” or without the trailer.

2. That aerodynamic “ bins” established for high-roof trucks be carried over to mid- and low-roof 

trucks rather than requiring testing for all low and mid roof trucks.

For both of the two above items, EPA agreed to evaluate testing data that is being collected as part of an 

aerodynamic drag testing program and to make a decision on both of the above. 

Last, with regard to selective enforcement audits, EMA/TMA asked that EPA use the test method the 

manufacturer uses in-house. The agencies agreed to consider this request.