

U.S. DEPARTMENT OF TRANSPORTATION

NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

1200 NEW JERSEY AVENUE SE.

WASHINGTON DC, 20590	UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF AIR AND RADIATION

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2000 TRAVERWOOD DRIVE

ANN ARBOR, MI  48105-2498



July 18, 2016

MEMORANDUM

SUBJECT:	Evaluation of Weight Reduction Distribution in Response to
Public Comments from Wabash National Corporation

FROM:	Jessica Brakora, Engineer, Assessment and Standards Division

Office of Transportation and Air Quality

TO:	Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for
Medium- and Heavy-Duty Engines and Vehicles - Phase 2 - Dockets
NHTSA-2014-0132 and EPA-HQ-OAR-2014-0827



The agencies received public comments from Wabash National Corporation
(Wabash) requesting that we remove the distribution of weight reduction
applied in GEM.  For tractors and trailers, GEM assigns 1/3 of any
weight reduction applied to increase the payload and the remaining 2/3
reduce the overall vehicle weight.  The agencies apply this strategy to
account for the nearly 1/3 of tractor-trailers that reach their weight
limit before they reach the volume capacity of their trailer
(weigh-out).  Wabash interpreted this strategy as a penalty, noting that
the full weight reduction is not being applied to the vehicle and the
model would not predict sufficient benefit.  However, the standards
adopted in this rulemaking account for payload (i.e., g CO2/ton-mi and
gallons/1000 ton-mi) and this memo demonstrates that this weight
reduction distribution will not negatively impact the results from the
model, and in some cases will even provide an additional benefit versus
simply reducing the overall vehicle weight.

The agencies used GEM to evaluate a long dry van (LDV) and a short dry
van (SDV).  For each trailer, we simulated a baseline case with no
weight reduction, and three cases with increasing weight reduction:  200
lb, 500 lb, and 1000 lb.  The first simulation used the standard weight
reduction strategy that applies 1/3 of the weight reduction to increased
payload.  The second simulation applied 100% of the weight reduction to
reducing the vehicle weight.    REF _Ref455670211 \h  Figure 1  and  
REF _Ref455670213 \h  Figure 2  show the results of these simulations. 
It can be seen in   REF _Ref455670211 \h  Figure 1  that the strategies
are very similar for long vans.  However, short trailers are more
sensitive to weight reduction, because their overall vehicle weight is
much lower than the long trailers.  As shown in   REF _Ref455670213 \h 
Figure 2 , fully applying the weight reduction to reducing the vehicle
weight results in a higher (worse) CO2 result for short vans.  

 

Figure   SEQ Figure \* ARABIC  1   Comparison of weight reduction
strategies for a long dry van simulated in GEM

 

Figure   SEQ Figure \* ARABIC  2   Comparison of weight reduction
strategies for a short dry van simulated in GEM

While exclusively reducing overall vehicle weight does reduce CO2
(comparing the 0 lb and 1000 lb weight reductions), we note that
applying additional payload (adding more to the denominator) also
decreases the result.  For short trailers, adding to the payload is more
effective and a difference is seen with a relatively small weight
reduction of 200 lb.  Long dry vans would likely need much higher weight
reduction values before the increased payload causes a distinct
difference between the two strategies.

Attachment: 
MemoAttachment_TrailerWeightReductionDistribution_Wabash.xlsx

Evaluation of Weight Reduction Distribution in Response to Public
Comments, Page   PAGE  2  of   NUMPAGES   2 

