The most recent 21st Century Truck Partnership (21CTP) white paper1 adopted the Environmental Protection Agency’s (EPA’s) Cd and Crr baselines from the proposed EPA/National Highway Traffic Safety Administration (NHTSA) greenhouse gas (GHG) rule that were to represent roughly the median of current in-use equipment for highway duty tractor-trailers with high-roof sleepers (identified in Table G-1) as “EPA GHG Rule Conventional High-Roof Average T-T.” These coefficients are higher than those used in previous Partnership documents and prevailing industry documents, which represented circa 2005 to 2009 production available designs and components, identified in Table G-1 as “NRC 21CTP Review, Phase 2.” See also footnote e in Table G-1 .
Notice for example, that the currently available EPA SmartWay aerodynamics and tires (0.59 and 0.0063) provide lower fuel consumption than is achievable with the Average T-T base coefficients in the EPA/NHTSA GHG rule (0.69 and supposed combination weighted 0.0077), by about 7 percent and 6 percent, respectively; 13 percent when combined.
1Received by the committee on March 17, 2011.
|Truck Configuration Description||Cd||Crr|
|1974 COE T-Tb||1.02||0.0103c|
|1974 COE T-T, Closed Gap, Trailer Skirts, Boat-Tailb||0.46|
|EPA Classic Conventional, Exterior Air Cleaners, Verticle Exhaust, Flat Bumber, No Aero Features T-T||0.77|
|EPA GHG Rule (CE-CERT) 2000’s Conventional High Roof T-T||0.74|
|EPA GHG Rule Conventional High-Roof Average T-T||0.69||0.0078||0.0082||0.0072d||0.0077|
|NRC 21CTP, Phase 2, Mid-2000s Conventional High Roof, pre-S/W T-Te||0.63||0.0068|
|EPA GHG Rule Conventional High-Roof SmartWay T-T||0.59||0.0059||0.0074||0.0053||0.0063|
|EPA GHG Rule Conventional High-Roof Advanced SmartWay T-T||0.55||0.0055|
|NRC 21CTP Review, Phase 2, Conventional High Roof, 2015-2020 T-T||0.45||0.0045|
NOTE: COE T-T: Cab Over Engine Tractor-Trailer. T-T: Tractor-Trailer. The Cds’ and the Crrs’ in the table are not derived from a consistent set of measurement or test procedures.
a Weightings: Steer (12), Drive (34), Trailer (34) reflect distribution of (80,000) lb Gross Vehicle Weight (GVW).
b K.R. Cooper, Commercial Vehicle Aerodynamic Drag Reduction: Historical Perspective as a Guide, The Aerodynamics of Heavy Vehicles: Trucks, Buses, and Trains, October 15, 2004. Springer.
c Based on bias ply tires.
d Assumed by National Research Council committee.
e Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and CO2 Emissions, NESCCAF/ICCT, Miller ed., October, 2009; and Cd same as the DOE 2006 21st Century Truck Roadmap and Technical White Papers. Doc No. 21CTP-003, December, Washington, D.C.